| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * linux/fs/namei.c |
| * |
| * Copyright (C) 1991, 1992 Linus Torvalds |
| */ |
| |
| /* |
| * Some corrections by tytso. |
| */ |
| |
| /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname |
| * lookup logic. |
| */ |
| /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture. |
| */ |
| |
| #include <linux/init.h> |
| #include <linux/export.h> |
| #include <linux/kernel.h> |
| #include <linux/slab.h> |
| #include <linux/fs.h> |
| #include <linux/namei.h> |
| #include <linux/pagemap.h> |
| #include <linux/fsnotify.h> |
| #include <linux/personality.h> |
| #include <linux/security.h> |
| #include <linux/ima.h> |
| #include <linux/syscalls.h> |
| #include <linux/mount.h> |
| #include <linux/audit.h> |
| #include <linux/capability.h> |
| #include <linux/file.h> |
| #include <linux/fcntl.h> |
| #include <linux/device_cgroup.h> |
| #include <linux/fs_struct.h> |
| #include <linux/posix_acl.h> |
| #include <linux/hash.h> |
| #include <linux/bitops.h> |
| #include <linux/init_task.h> |
| #include <linux/uaccess.h> |
| |
| #include "internal.h" |
| #include "mount.h" |
| |
| /* [Feb-1997 T. Schoebel-Theuer] |
| * Fundamental changes in the pathname lookup mechanisms (namei) |
| * were necessary because of omirr. The reason is that omirr needs |
| * to know the _real_ pathname, not the user-supplied one, in case |
| * of symlinks (and also when transname replacements occur). |
| * |
| * The new code replaces the old recursive symlink resolution with |
| * an iterative one (in case of non-nested symlink chains). It does |
| * this with calls to <fs>_follow_link(). |
| * As a side effect, dir_namei(), _namei() and follow_link() are now |
| * replaced with a single function lookup_dentry() that can handle all |
| * the special cases of the former code. |
| * |
| * With the new dcache, the pathname is stored at each inode, at least as |
| * long as the refcount of the inode is positive. As a side effect, the |
| * size of the dcache depends on the inode cache and thus is dynamic. |
| * |
| * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink |
| * resolution to correspond with current state of the code. |
| * |
| * Note that the symlink resolution is not *completely* iterative. |
| * There is still a significant amount of tail- and mid- recursion in |
| * the algorithm. Also, note that <fs>_readlink() is not used in |
| * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink() |
| * may return different results than <fs>_follow_link(). Many virtual |
| * filesystems (including /proc) exhibit this behavior. |
| */ |
| |
| /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation: |
| * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL |
| * and the name already exists in form of a symlink, try to create the new |
| * name indicated by the symlink. The old code always complained that the |
| * name already exists, due to not following the symlink even if its target |
| * is nonexistent. The new semantics affects also mknod() and link() when |
| * the name is a symlink pointing to a non-existent name. |
| * |
| * I don't know which semantics is the right one, since I have no access |
| * to standards. But I found by trial that HP-UX 9.0 has the full "new" |
| * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the |
| * "old" one. Personally, I think the new semantics is much more logical. |
| * Note that "ln old new" where "new" is a symlink pointing to a non-existing |
| * file does succeed in both HP-UX and SunOs, but not in Solaris |
| * and in the old Linux semantics. |
| */ |
| |
| /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink |
| * semantics. See the comments in "open_namei" and "do_link" below. |
| * |
| * [10-Sep-98 Alan Modra] Another symlink change. |
| */ |
| |
| /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks: |
| * inside the path - always follow. |
| * in the last component in creation/removal/renaming - never follow. |
| * if LOOKUP_FOLLOW passed - follow. |
| * if the pathname has trailing slashes - follow. |
| * otherwise - don't follow. |
| * (applied in that order). |
| * |
| * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT |
| * restored for 2.4. This is the last surviving part of old 4.2BSD bug. |
| * During the 2.4 we need to fix the userland stuff depending on it - |
| * hopefully we will be able to get rid of that wart in 2.5. So far only |
| * XEmacs seems to be relying on it... |
| */ |
| /* |
| * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland) |
| * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives |
| * any extra contention... |
| */ |
| |
| /* In order to reduce some races, while at the same time doing additional |
| * checking and hopefully speeding things up, we copy filenames to the |
| * kernel data space before using them.. |
| * |
| * POSIX.1 2.4: an empty pathname is invalid (ENOENT). |
| * PATH_MAX includes the nul terminator --RR. |
| */ |
| |
| #define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname)) |
| |
| struct filename * |
| getname_flags(const char __user *filename, int flags, int *empty) |
| { |
| struct filename *result; |
| char *kname; |
| int len; |
| |
| result = audit_reusename(filename); |
| if (result) |
| return result; |
| |
| result = __getname(); |
| if (unlikely(!result)) |
| return ERR_PTR(-ENOMEM); |
| |
| /* |
| * First, try to embed the struct filename inside the names_cache |
| * allocation |
| */ |
| kname = (char *)result->iname; |
| result->name = kname; |
| |
| len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX); |
| if (unlikely(len < 0)) { |
| __putname(result); |
| return ERR_PTR(len); |
| } |
| |
| /* |
| * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a |
| * separate struct filename so we can dedicate the entire |
| * names_cache allocation for the pathname, and re-do the copy from |
| * userland. |
| */ |
| if (unlikely(len == EMBEDDED_NAME_MAX)) { |
| const size_t size = offsetof(struct filename, iname[1]); |
| kname = (char *)result; |
| |
| /* |
| * size is chosen that way we to guarantee that |
| * result->iname[0] is within the same object and that |
| * kname can't be equal to result->iname, no matter what. |
| */ |
| result = kzalloc(size, GFP_KERNEL); |
| if (unlikely(!result)) { |
| __putname(kname); |
| return ERR_PTR(-ENOMEM); |
| } |
| result->name = kname; |
| len = strncpy_from_user(kname, filename, PATH_MAX); |
| if (unlikely(len < 0)) { |
| __putname(kname); |
| kfree(result); |
| return ERR_PTR(len); |
| } |
| if (unlikely(len == PATH_MAX)) { |
| __putname(kname); |
| kfree(result); |
| return ERR_PTR(-ENAMETOOLONG); |
| } |
| } |
| |
| result->refcnt = 1; |
| /* The empty path is special. */ |
| if (unlikely(!len)) { |
| if (empty) |
| *empty = 1; |
| if (!(flags & LOOKUP_EMPTY)) { |
| putname(result); |
| return ERR_PTR(-ENOENT); |
| } |
| } |
| |
| result->uptr = filename; |
| result->aname = NULL; |
| audit_getname(result); |
| return result; |
| } |
| |
| struct filename * |
| getname(const char __user * filename) |
| { |
| return getname_flags(filename, 0, NULL); |
| } |
| |
| struct filename * |
| getname_kernel(const char * filename) |
| { |
| struct filename *result; |
| int len = strlen(filename) + 1; |
| |
| result = __getname(); |
| if (unlikely(!result)) |
| return ERR_PTR(-ENOMEM); |
| |
| if (len <= EMBEDDED_NAME_MAX) { |
| result->name = (char *)result->iname; |
| } else if (len <= PATH_MAX) { |
| struct filename *tmp; |
| |
| tmp = kmalloc(sizeof(*tmp), GFP_KERNEL); |
| if (unlikely(!tmp)) { |
| __putname(result); |
| return ERR_PTR(-ENOMEM); |
| } |
| tmp->name = (char *)result; |
| result = tmp; |
| } else { |
| __putname(result); |
| return ERR_PTR(-ENAMETOOLONG); |
| } |
| memcpy((char *)result->name, filename, len); |
| result->uptr = NULL; |
| result->aname = NULL; |
| result->refcnt = 1; |
| audit_getname(result); |
| |
| return result; |
| } |
| |
| void putname(struct filename *name) |
| { |
| BUG_ON(name->refcnt <= 0); |
| |
| if (--name->refcnt > 0) |
| return; |
| |
| if (name->name != name->iname) { |
| __putname(name->name); |
| kfree(name); |
| } else |
| __putname(name); |
| } |
| |
| static int check_acl(struct inode *inode, int mask) |
| { |
| #ifdef CONFIG_FS_POSIX_ACL |
| struct posix_acl *acl; |
| |
| if (mask & MAY_NOT_BLOCK) { |
| acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS); |
| if (!acl) |
| return -EAGAIN; |
| /* no ->get_acl() calls in RCU mode... */ |
| if (is_uncached_acl(acl)) |
| return -ECHILD; |
| return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK); |
| } |
| |
| acl = get_acl(inode, ACL_TYPE_ACCESS); |
| if (IS_ERR(acl)) |
| return PTR_ERR(acl); |
| if (acl) { |
| int error = posix_acl_permission(inode, acl, mask); |
| posix_acl_release(acl); |
| return error; |
| } |
| #endif |
| |
| return -EAGAIN; |
| } |
| |
| /* |
| * This does the basic permission checking |
| */ |
| static int acl_permission_check(struct inode *inode, int mask) |
| { |
| unsigned int mode = inode->i_mode; |
| |
| if (likely(uid_eq(current_fsuid(), inode->i_uid))) |
| mode >>= 6; |
| else { |
| if (IS_POSIXACL(inode) && (mode & S_IRWXG)) { |
| int error = check_acl(inode, mask); |
| if (error != -EAGAIN) |
| return error; |
| } |
| |
| if (in_group_p(inode->i_gid)) |
| mode >>= 3; |
| } |
| |
| /* |
| * If the DACs are ok we don't need any capability check. |
| */ |
| if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0) |
| return 0; |
| return -EACCES; |
| } |
| |
| /** |
| * generic_permission - check for access rights on a Posix-like filesystem |
| * @inode: inode to check access rights for |
| * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...) |
| * |
| * Used to check for read/write/execute permissions on a file. |
| * We use "fsuid" for this, letting us set arbitrary permissions |
| * for filesystem access without changing the "normal" uids which |
| * are used for other things. |
| * |
| * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk |
| * request cannot be satisfied (eg. requires blocking or too much complexity). |
| * It would then be called again in ref-walk mode. |
| */ |
| int generic_permission(struct inode *inode, int mask) |
| { |
| int ret; |
| |
| /* |
| * Do the basic permission checks. |
| */ |
| ret = acl_permission_check(inode, mask); |
| if (ret != -EACCES) |
| return ret; |
| |
| if (S_ISDIR(inode->i_mode)) { |
| /* DACs are overridable for directories */ |
| if (!(mask & MAY_WRITE)) |
| if (capable_wrt_inode_uidgid(inode, |
| CAP_DAC_READ_SEARCH)) |
| return 0; |
| if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) |
| return 0; |
| return -EACCES; |
| } |
| |
| /* |
| * Searching includes executable on directories, else just read. |
| */ |
| mask &= MAY_READ | MAY_WRITE | MAY_EXEC; |
| if (mask == MAY_READ) |
| if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH)) |
| return 0; |
| /* |
| * Read/write DACs are always overridable. |
| * Executable DACs are overridable when there is |
| * at least one exec bit set. |
| */ |
| if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) |
| if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) |
| return 0; |
| |
| return -EACCES; |
| } |
| EXPORT_SYMBOL(generic_permission); |
| |
| /* |
| * We _really_ want to just do "generic_permission()" without |
| * even looking at the inode->i_op values. So we keep a cache |
| * flag in inode->i_opflags, that says "this has not special |
| * permission function, use the fast case". |
| */ |
| static inline int do_inode_permission(struct inode *inode, int mask) |
| { |
| if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) { |
| if (likely(inode->i_op->permission)) |
| return inode->i_op->permission(inode, mask); |
| |
| /* This gets set once for the inode lifetime */ |
| spin_lock(&inode->i_lock); |
| inode->i_opflags |= IOP_FASTPERM; |
| spin_unlock(&inode->i_lock); |
| } |
| return generic_permission(inode, mask); |
| } |
| |
| /** |
| * __inode_permission - Check for access rights to a given inode |
| * @inode: Inode to check permission on |
| * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
| * |
| * Check for read/write/execute permissions on an inode. |
| * |
| * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. |
| * |
| * This does not check for a read-only file system. You probably want |
| * inode_permission(). |
| */ |
| int __inode_permission(struct inode *inode, int mask) |
| { |
| int retval; |
| |
| if (unlikely(mask & MAY_WRITE)) { |
| /* |
| * Nobody gets write access to an immutable file. |
| */ |
| if (IS_IMMUTABLE(inode)) |
| return -EPERM; |
| |
| /* |
| * Updating mtime will likely cause i_uid and i_gid to be |
| * written back improperly if their true value is unknown |
| * to the vfs. |
| */ |
| if (HAS_UNMAPPED_ID(inode)) |
| return -EACCES; |
| } |
| |
| retval = do_inode_permission(inode, mask); |
| if (retval) |
| return retval; |
| |
| retval = devcgroup_inode_permission(inode, mask); |
| if (retval) |
| return retval; |
| |
| return security_inode_permission(inode, mask); |
| } |
| EXPORT_SYMBOL(__inode_permission); |
| |
| /** |
| * sb_permission - Check superblock-level permissions |
| * @sb: Superblock of inode to check permission on |
| * @inode: Inode to check permission on |
| * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
| * |
| * Separate out file-system wide checks from inode-specific permission checks. |
| */ |
| static int sb_permission(struct super_block *sb, struct inode *inode, int mask) |
| { |
| if (unlikely(mask & MAY_WRITE)) { |
| umode_t mode = inode->i_mode; |
| |
| /* Nobody gets write access to a read-only fs. */ |
| if (sb_rdonly(sb) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) |
| return -EROFS; |
| } |
| return 0; |
| } |
| |
| /** |
| * inode_permission - Check for access rights to a given inode |
| * @inode: Inode to check permission on |
| * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
| * |
| * Check for read/write/execute permissions on an inode. We use fs[ug]id for |
| * this, letting us set arbitrary permissions for filesystem access without |
| * changing the "normal" UIDs which are used for other things. |
| * |
| * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. |
| */ |
| int inode_permission(struct inode *inode, int mask) |
| { |
| int retval; |
| |
| retval = sb_permission(inode->i_sb, inode, mask); |
| if (retval) |
| return retval; |
| return __inode_permission(inode, mask); |
| } |
| EXPORT_SYMBOL(inode_permission); |
| |
| /** |
| * path_get - get a reference to a path |
| * @path: path to get the reference to |
| * |
| * Given a path increment the reference count to the dentry and the vfsmount. |
| */ |
| void path_get(const struct path *path) |
| { |
| mntget(path->mnt); |
| dget(path->dentry); |
| } |
| EXPORT_SYMBOL(path_get); |
| |
| /** |
| * path_put - put a reference to a path |
| * @path: path to put the reference to |
| * |
| * Given a path decrement the reference count to the dentry and the vfsmount. |
| */ |
| void path_put(const struct path *path) |
| { |
| dput(path->dentry); |
| mntput(path->mnt); |
| } |
| EXPORT_SYMBOL(path_put); |
| |
| #define EMBEDDED_LEVELS 2 |
| struct nameidata { |
| struct path path; |
| struct qstr last; |
| struct path root; |
| struct inode *inode; /* path.dentry.d_inode */ |
| unsigned int flags; |
| unsigned seq, m_seq; |
| int last_type; |
| unsigned depth; |
| int total_link_count; |
| struct saved { |
| struct path link; |
| struct delayed_call done; |
| const char *name; |
| unsigned seq; |
| } *stack, internal[EMBEDDED_LEVELS]; |
| struct filename *name; |
| struct nameidata *saved; |
| struct inode *link_inode; |
| unsigned root_seq; |
| int dfd; |
| } __randomize_layout; |
| |
| static void set_nameidata(struct nameidata *p, int dfd, struct filename *name) |
| { |
| struct nameidata *old = current->nameidata; |
| p->stack = p->internal; |
| p->dfd = dfd; |
| p->name = name; |
| p->total_link_count = old ? old->total_link_count : 0; |
| p->saved = old; |
| current->nameidata = p; |
| } |
| |
| static void restore_nameidata(void) |
| { |
| struct nameidata *now = current->nameidata, *old = now->saved; |
| |
| current->nameidata = old; |
| if (old) |
| old->total_link_count = now->total_link_count; |
| if (now->stack != now->internal) |
| kfree(now->stack); |
| } |
| |
| static int __nd_alloc_stack(struct nameidata *nd) |
| { |
| struct saved *p; |
| |
| if (nd->flags & LOOKUP_RCU) { |
| p= kmalloc(MAXSYMLINKS * sizeof(struct saved), |
| GFP_ATOMIC); |
| if (unlikely(!p)) |
| return -ECHILD; |
| } else { |
| p= kmalloc(MAXSYMLINKS * sizeof(struct saved), |
| GFP_KERNEL); |
| if (unlikely(!p)) |
| return -ENOMEM; |
| } |
| memcpy(p, nd->internal, sizeof(nd->internal)); |
| nd->stack = p; |
| return 0; |
| } |
| |
| /** |
| * path_connected - Verify that a path->dentry is below path->mnt.mnt_root |
| * @path: nameidate to verify |
| * |
| * Rename can sometimes move a file or directory outside of a bind |
| * mount, path_connected allows those cases to be detected. |
| */ |
| static bool path_connected(const struct path *path) |
| { |
| struct vfsmount *mnt = path->mnt; |
| |
| /* Only bind mounts can have disconnected paths */ |
| if (mnt->mnt_root == mnt->mnt_sb->s_root) |
| return true; |
| |
| return is_subdir(path->dentry, mnt->mnt_root); |
| } |
| |
| static inline int nd_alloc_stack(struct nameidata *nd) |
| { |
| if (likely(nd->depth != EMBEDDED_LEVELS)) |
| return 0; |
| if (likely(nd->stack != nd->internal)) |
| return 0; |
| return __nd_alloc_stack(nd); |
| } |
| |
| static void drop_links(struct nameidata *nd) |
| { |
| int i = nd->depth; |
| while (i--) { |
| struct saved *last = nd->stack + i; |
| do_delayed_call(&last->done); |
| clear_delayed_call(&last->done); |
| } |
| } |
| |
| static void terminate_walk(struct nameidata *nd) |
| { |
| drop_links(nd); |
| if (!(nd->flags & LOOKUP_RCU)) { |
| int i; |
| path_put(&nd->path); |
| for (i = 0; i < nd->depth; i++) |
| path_put(&nd->stack[i].link); |
| if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { |
| path_put(&nd->root); |
| nd->root.mnt = NULL; |
| } |
| } else { |
| nd->flags &= ~LOOKUP_RCU; |
| if (!(nd->flags & LOOKUP_ROOT)) |
| nd->root.mnt = NULL; |
| rcu_read_unlock(); |
| } |
| nd->depth = 0; |
| } |
| |
| /* path_put is needed afterwards regardless of success or failure */ |
| static bool legitimize_path(struct nameidata *nd, |
| struct path *path, unsigned seq) |
| { |
| int res = __legitimize_mnt(path->mnt, nd->m_seq); |
| if (unlikely(res)) { |
| if (res > 0) |
| path->mnt = NULL; |
| path->dentry = NULL; |
| return false; |
| } |
| if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) { |
| path->dentry = NULL; |
| return false; |
| } |
| return !read_seqcount_retry(&path->dentry->d_seq, seq); |
| } |
| |
| static bool legitimize_links(struct nameidata *nd) |
| { |
| int i; |
| for (i = 0; i < nd->depth; i++) { |
| struct saved *last = nd->stack + i; |
| if (unlikely(!legitimize_path(nd, &last->link, last->seq))) { |
| drop_links(nd); |
| nd->depth = i + 1; |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| /* |
| * Path walking has 2 modes, rcu-walk and ref-walk (see |
| * Documentation/filesystems/path-lookup.txt). In situations when we can't |
| * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab |
| * normal reference counts on dentries and vfsmounts to transition to ref-walk |
| * mode. Refcounts are grabbed at the last known good point before rcu-walk |
| * got stuck, so ref-walk may continue from there. If this is not successful |
| * (eg. a seqcount has changed), then failure is returned and it's up to caller |
| * to restart the path walk from the beginning in ref-walk mode. |
| */ |
| |
| /** |
| * unlazy_walk - try to switch to ref-walk mode. |
| * @nd: nameidata pathwalk data |
| * Returns: 0 on success, -ECHILD on failure |
| * |
| * unlazy_walk attempts to legitimize the current nd->path and nd->root |
| * for ref-walk mode. |
| * Must be called from rcu-walk context. |
| * Nothing should touch nameidata between unlazy_walk() failure and |
| * terminate_walk(). |
| */ |
| static int unlazy_walk(struct nameidata *nd) |
| { |
| struct dentry *parent = nd->path.dentry; |
| |
| BUG_ON(!(nd->flags & LOOKUP_RCU)); |
| |
| nd->flags &= ~LOOKUP_RCU; |
| if (unlikely(!legitimize_links(nd))) |
| goto out2; |
| if (unlikely(!legitimize_path(nd, &nd->path, nd->seq))) |
| goto out1; |
| if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { |
| if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq))) |
| goto out; |
| } |
| rcu_read_unlock(); |
| BUG_ON(nd->inode != parent->d_inode); |
| return 0; |
| |
| out2: |
| nd->path.mnt = NULL; |
| nd->path.dentry = NULL; |
| out1: |
| if (!(nd->flags & LOOKUP_ROOT)) |
| nd->root.mnt = NULL; |
| out: |
| rcu_read_unlock(); |
| return -ECHILD; |
| } |
| |
| /** |
| * unlazy_child - try to switch to ref-walk mode. |
| * @nd: nameidata pathwalk data |
| * @dentry: child of nd->path.dentry |
| * @seq: seq number to check dentry against |
| * Returns: 0 on success, -ECHILD on failure |
| * |
| * unlazy_child attempts to legitimize the current nd->path, nd->root and dentry |
| * for ref-walk mode. @dentry must be a path found by a do_lookup call on |
| * @nd. Must be called from rcu-walk context. |
| * Nothing should touch nameidata between unlazy_child() failure and |
| * terminate_walk(). |
| */ |
| static int unlazy_child(struct nameidata *nd, struct dentry *dentry, unsigned seq) |
| { |
| BUG_ON(!(nd->flags & LOOKUP_RCU)); |
| |
| nd->flags &= ~LOOKUP_RCU; |
| if (unlikely(!legitimize_links(nd))) |
| goto out2; |
| if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq))) |
| goto out2; |
| if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref))) |
| goto out1; |
| |
| /* |
| * We need to move both the parent and the dentry from the RCU domain |
| * to be properly refcounted. And the sequence number in the dentry |
| * validates *both* dentry counters, since we checked the sequence |
| * number of the parent after we got the child sequence number. So we |
| * know the parent must still be valid if the child sequence number is |
| */ |
| if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) |
| goto out; |
| if (unlikely(read_seqcount_retry(&dentry->d_seq, seq))) { |
| rcu_read_unlock(); |
| dput(dentry); |
| goto drop_root_mnt; |
| } |
| /* |
| * Sequence counts matched. Now make sure that the root is |
| * still valid and get it if required. |
| */ |
| if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { |
| if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq))) { |
| rcu_read_unlock(); |
| dput(dentry); |
| return -ECHILD; |
| } |
| } |
| |
| rcu_read_unlock(); |
| return 0; |
| |
| out2: |
| nd->path.mnt = NULL; |
| out1: |
| nd->path.dentry = NULL; |
| out: |
| rcu_read_unlock(); |
| drop_root_mnt: |
| if (!(nd->flags & LOOKUP_ROOT)) |
| nd->root.mnt = NULL; |
| return -ECHILD; |
| } |
| |
| static inline int d_revalidate(struct dentry *dentry, unsigned int flags) |
| { |
| if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) |
| return dentry->d_op->d_revalidate(dentry, flags); |
| else |
| return 1; |
| } |
| |
| /** |
| * complete_walk - successful completion of path walk |
| * @nd: pointer nameidata |
| * |
| * If we had been in RCU mode, drop out of it and legitimize nd->path. |
| * Revalidate the final result, unless we'd already done that during |
| * the path walk or the filesystem doesn't ask for it. Return 0 on |
| * success, -error on failure. In case of failure caller does not |
| * need to drop nd->path. |
| */ |
| static int complete_walk(struct nameidata *nd) |
| { |
| struct dentry *dentry = nd->path.dentry; |
| int status; |
| |
| if (nd->flags & LOOKUP_RCU) { |
| if (!(nd->flags & LOOKUP_ROOT)) |
| nd->root.mnt = NULL; |
| if (unlikely(unlazy_walk(nd))) |
| return -ECHILD; |
| } |
| |
| if (likely(!(nd->flags & LOOKUP_JUMPED))) |
| return 0; |
| |
| if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE))) |
| return 0; |
| |
| status = dentry->d_op->d_weak_revalidate(dentry, nd->flags); |
| if (status > 0) |
| return 0; |
| |
| if (!status) |
| status = -ESTALE; |
| |
| return status; |
| } |
| |
| static void set_root(struct nameidata *nd) |
| { |
| struct fs_struct *fs = current->fs; |
| |
| if (nd->flags & LOOKUP_RCU) { |
| unsigned seq; |
| |
| do { |
| seq = read_seqcount_begin(&fs->seq); |
| nd->root = fs->root; |
| nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq); |
| } while (read_seqcount_retry(&fs->seq, seq)); |
| } else { |
| get_fs_root(fs, &nd->root); |
| } |
| } |
| |
| static void path_put_conditional(struct path *path, struct nameidata *nd) |
| { |
| dput(path->dentry); |
| if (path->mnt != nd->path.mnt) |
| mntput(path->mnt); |
| } |
| |
| static inline void path_to_nameidata(const struct path *path, |
| struct nameidata *nd) |
| { |
| if (!(nd->flags & LOOKUP_RCU)) { |
| dput(nd->path.dentry); |
| if (nd->path.mnt != path->mnt) |
| mntput(nd->path.mnt); |
| } |
| nd->path.mnt = path->mnt; |
| nd->path.dentry = path->dentry; |
| } |
| |
| static int nd_jump_root(struct nameidata *nd) |
| { |
| if (nd->flags & LOOKUP_RCU) { |
| struct dentry *d; |
| nd->path = nd->root; |
| d = nd->path.dentry; |
| nd->inode = d->d_inode; |
| nd->seq = nd->root_seq; |
| if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq))) |
| return -ECHILD; |
| } else { |
| path_put(&nd->path); |
| nd->path = nd->root; |
| path_get(&nd->path); |
| nd->inode = nd->path.dentry->d_inode; |
| } |
| nd->flags |= LOOKUP_JUMPED; |
| return 0; |
| } |
| |
| /* |
| * Helper to directly jump to a known parsed path from ->get_link, |
| * caller must have taken a reference to path beforehand. |
| */ |
| void nd_jump_link(struct path *path) |
| { |
| struct nameidata *nd = current->nameidata; |
| path_put(&nd->path); |
| |
| nd->path = *path; |
| nd->inode = nd->path.dentry->d_inode; |
| nd->flags |= LOOKUP_JUMPED; |
| } |
| |
| static inline void put_link(struct nameidata *nd) |
| { |
| struct saved *last = nd->stack + --nd->depth; |
| do_delayed_call(&last->done); |
| if (!(nd->flags & LOOKUP_RCU)) |
| path_put(&last->link); |
| } |
| |
| int sysctl_protected_symlinks __read_mostly = 0; |
| int sysctl_protected_hardlinks __read_mostly = 0; |
| |
| /** |
| * may_follow_link - Check symlink following for unsafe situations |
| * @nd: nameidata pathwalk data |
| * |
| * In the case of the sysctl_protected_symlinks sysctl being enabled, |
| * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is |
| * in a sticky world-writable directory. This is to protect privileged |
| * processes from failing races against path names that may change out |
| * from under them by way of other users creating malicious symlinks. |
| * It will permit symlinks to be followed only when outside a sticky |
| * world-writable directory, or when the uid of the symlink and follower |
| * match, or when the directory owner matches the symlink's owner. |
| * |
| * Returns 0 if following the symlink is allowed, -ve on error. |
| */ |
| static inline int may_follow_link(struct nameidata *nd) |
| { |
| const struct inode *inode; |
| const struct inode *parent; |
| kuid_t puid; |
| |
| if (!sysctl_protected_symlinks) |
| return 0; |
| |
| /* Allowed if owner and follower match. */ |
| inode = nd->link_inode; |
| if (uid_eq(current_cred()->fsuid, inode->i_uid)) |
| return 0; |
| |
| /* Allowed if parent directory not sticky and world-writable. */ |
| parent = nd->inode; |
| if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH)) |
| return 0; |
| |
| /* Allowed if parent directory and link owner match. */ |
| puid = parent->i_uid; |
| if (uid_valid(puid) && uid_eq(puid, inode->i_uid)) |
| return 0; |
| |
| if (nd->flags & LOOKUP_RCU) |
| return -ECHILD; |
| |
| audit_log_link_denied("follow_link", &nd->stack[0].link); |
| return -EACCES; |
| } |
| |
| /** |
| * safe_hardlink_source - Check for safe hardlink conditions |
| * @inode: the source inode to hardlink from |
| * |
| * Return false if at least one of the following conditions: |
| * - inode is not a regular file |
| * - inode is setuid |
| * - inode is setgid and group-exec |
| * - access failure for read and write |
| * |
| * Otherwise returns true. |
| */ |
| static bool safe_hardlink_source(struct inode *inode) |
| { |
| umode_t mode = inode->i_mode; |
| |
| /* Special files should not get pinned to the filesystem. */ |
| if (!S_ISREG(mode)) |
| return false; |
| |
| /* Setuid files should not get pinned to the filesystem. */ |
| if (mode & S_ISUID) |
| return false; |
| |
| /* Executable setgid files should not get pinned to the filesystem. */ |
| if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) |
| return false; |
| |
| /* Hardlinking to unreadable or unwritable sources is dangerous. */ |
| if (inode_permission(inode, MAY_READ | MAY_WRITE)) |
| return false; |
| |
| return true; |
| } |
| |
| /** |
| * may_linkat - Check permissions for creating a hardlink |
| * @link: the source to hardlink from |
| * |
| * Block hardlink when all of: |
| * - sysctl_protected_hardlinks enabled |
| * - fsuid does not match inode |
| * - hardlink source is unsafe (see safe_hardlink_source() above) |
| * - not CAP_FOWNER in a namespace with the inode owner uid mapped |
| * |
| * Returns 0 if successful, -ve on error. |
| */ |
| static int may_linkat(struct path *link) |
| { |
| struct inode *inode; |
| |
| if (!sysctl_protected_hardlinks) |
| return 0; |
| |
| inode = link->dentry->d_inode; |
| |
| /* Source inode owner (or CAP_FOWNER) can hardlink all they like, |
| * otherwise, it must be a safe source. |
| */ |
| if (safe_hardlink_source(inode) || inode_owner_or_capable(inode)) |
| return 0; |
| |
| audit_log_link_denied("linkat", link); |
| return -EPERM; |
| } |
| |
| static __always_inline |
| const char *get_link(struct nameidata *nd) |
| { |
| struct saved *last = nd->stack + nd->depth - 1; |
| struct dentry *dentry = last->link.dentry; |
| struct inode *inode = nd->link_inode; |
| int error; |
| const char *res; |
| |
| if (!(nd->flags & LOOKUP_RCU)) { |
| touch_atime(&last->link); |
| cond_resched(); |
| } else if (atime_needs_update_rcu(&last->link, inode)) { |
| if (unlikely(unlazy_walk(nd))) |
| return ERR_PTR(-ECHILD); |
| touch_atime(&last->link); |
| } |
| |
| error = security_inode_follow_link(dentry, inode, |
| nd->flags & LOOKUP_RCU); |
| if (unlikely(error)) |
| return ERR_PTR(error); |
| |
| nd->last_type = LAST_BIND; |
| res = inode->i_link; |
| if (!res) { |
| const char * (*get)(struct dentry *, struct inode *, |
| struct delayed_call *); |
| get = inode->i_op->get_link; |
| if (nd->flags & LOOKUP_RCU) { |
| res = get(NULL, inode, &last->done); |
| if (res == ERR_PTR(-ECHILD)) { |
| if (unlikely(unlazy_walk(nd))) |
| return ERR_PTR(-ECHILD); |
| res = get(dentry, inode, &last->done); |
| } |
| } else { |
| res = get(dentry, inode, &last->done); |
| } |
| if (IS_ERR_OR_NULL(res)) |
| return res; |
| } |
| if (*res == '/') { |
| if (!nd->root.mnt) |
| set_root(nd); |
| if (unlikely(nd_jump_root(nd))) |
| return ERR_PTR(-ECHILD); |
| while (unlikely(*++res == '/')) |
| ; |
| } |
| if (!*res) |
| res = NULL; |
| return res; |
| } |
| |
| /* |
| * follow_up - Find the mountpoint of path's vfsmount |
| * |
| * Given a path, find the mountpoint of its source file system. |
| * Replace @path with the path of the mountpoint in the parent mount. |
| * Up is towards /. |
| * |
| * Return 1 if we went up a level and 0 if we were already at the |
| * root. |
| */ |
| int follow_up(struct path *path) |
| { |
| struct mount *mnt = real_mount(path->mnt); |
| struct mount *parent; |
| struct dentry *mountpoint; |
| |
| read_seqlock_excl(&mount_lock); |
| parent = mnt->mnt_parent; |
| if (parent == mnt) { |
| read_sequnlock_excl(&mount_lock); |
| return 0; |
| } |
| mntget(&parent->mnt); |
| mountpoint = dget(mnt->mnt_mountpoint); |
| read_sequnlock_excl(&mount_lock); |
| dput(path->dentry); |
| path->dentry = mountpoint; |
| mntput(path->mnt); |
| path->mnt = &parent->mnt; |
| return 1; |
| } |
| EXPORT_SYMBOL(follow_up); |
| |
| /* |
| * Perform an automount |
| * - return -EISDIR to tell follow_managed() to stop and return the path we |
| * were called with. |
| */ |
| static int follow_automount(struct path *path, struct nameidata *nd, |
| bool *need_mntput) |
| { |
| struct vfsmount *mnt; |
| int err; |
| |
| if (!path->dentry->d_op || !path->dentry->d_op->d_automount) |
| return -EREMOTE; |
| |
| /* We don't want to mount if someone's just doing a stat - |
| * unless they're stat'ing a directory and appended a '/' to |
| * the name. |
| * |
| * We do, however, want to mount if someone wants to open or |
| * create a file of any type under the mountpoint, wants to |
| * traverse through the mountpoint or wants to open the |
| * mounted directory. Also, autofs may mark negative dentries |
| * as being automount points. These will need the attentions |
| * of the daemon to instantiate them before they can be used. |
| */ |
| if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | |
| LOOKUP_OPEN | LOOKUP_CREATE | |
| LOOKUP_AUTOMOUNT))) { |
| /* Positive dentry that isn't meant to trigger an |
| * automount, EISDIR will allow it to be used, |
| * otherwise there's no mount here "now" so return |
| * ENOENT. |
| */ |
| if (path->dentry->d_inode) |
| return -EISDIR; |
| else |
| return -ENOENT; |
| } |
| |
| if (path->dentry->d_sb->s_user_ns != &init_user_ns) |
| return -EACCES; |
| |
| nd->total_link_count++; |
| if (nd->total_link_count >= 40) |
| return -ELOOP; |
| |
| mnt = path->dentry->d_op->d_automount(path); |
| if (IS_ERR(mnt)) { |
| /* |
| * The filesystem is allowed to return -EISDIR here to indicate |
| * it doesn't want to automount. For instance, autofs would do |
| * this so that its userspace daemon can mount on this dentry. |
| * |
| * However, we can only permit this if it's a terminal point in |
| * the path being looked up; if it wasn't then the remainder of |
| * the path is inaccessible and we should say so. |
| */ |
| if (PTR_ERR(mnt) == -EISDIR && (nd->flags & LOOKUP_PARENT)) |
| return -EREMOTE; |
| return PTR_ERR(mnt); |
| } |
| |
| if (!mnt) /* mount collision */ |
| return 0; |
| |
| if (!*need_mntput) { |
| /* lock_mount() may release path->mnt on error */ |
| mntget(path->mnt); |
| *need_mntput = true; |
| } |
| err = finish_automount(mnt, path); |
| |
| switch (err) { |
| case -EBUSY: |
| /* Someone else made a mount here whilst we were busy */ |
| return 0; |
| case 0: |
| path_put(path); |
| path->mnt = mnt; |
| path->dentry = dget(mnt->mnt_root); |
| return 0; |
| default: |
| return err; |
| } |
| |
| } |
| |
| /* |
| * Handle a dentry that is managed in some way. |
| * - Flagged for transit management (autofs) |
| * - Flagged as mountpoint |
| * - Flagged as automount point |
| * |
| * This may only be called in refwalk mode. |
| * |
| * Serialization is taken care of in namespace.c |
| */ |
| static int follow_managed(struct path *path, struct nameidata *nd) |
| { |
| struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */ |
| unsigned managed; |
| bool need_mntput = false; |
| int ret = 0; |
| |
| /* Given that we're not holding a lock here, we retain the value in a |
| * local variable for each dentry as we look at it so that we don't see |
| * the components of that value change under us */ |
| while (managed = ACCESS_ONCE(path->dentry->d_flags), |
| managed &= DCACHE_MANAGED_DENTRY, |
| unlikely(managed != 0)) { |
| /* Allow the filesystem to manage the transit without i_mutex |
| * being held. */ |
| if (managed & DCACHE_MANAGE_TRANSIT) { |
| BUG_ON(!path->dentry->d_op); |
| BUG_ON(!path->dentry->d_op->d_manage); |
| ret = path->dentry->d_op->d_manage(path, false); |
| if (ret < 0) |
| break; |
| } |
| |
| /* Transit to a mounted filesystem. */ |
| if (managed & DCACHE_MOUNTED) { |
| struct vfsmount *mounted = lookup_mnt(path); |
| if (mounted) { |
| dput(path->dentry); |
| if (need_mntput) |
| mntput(path->mnt); |
| path->mnt = mounted; |
| path->dentry = dget(mounted->mnt_root); |
| need_mntput = true; |
| continue; |
| } |
| |
| /* Something is mounted on this dentry in another |
| * namespace and/or whatever was mounted there in this |
| * namespace got unmounted before lookup_mnt() could |
| * get it */ |
| } |
| |
| /* Handle an automount point */ |
| if (managed & DCACHE_NEED_AUTOMOUNT) { |
| ret = follow_automount(path, nd, &need_mntput); |
| if (ret < 0) |
| break; |
| continue; |
| } |
| |
| /* We didn't change the current path point */ |
| break; |
| } |
| |
| if (need_mntput && path->mnt == mnt) |
| mntput(path->mnt); |
| if (ret == -EISDIR || !ret) |
| ret = 1; |
| if (need_mntput) |
| nd->flags |= LOOKUP_JUMPED; |
| if (unlikely(ret < 0)) |
| path_put_conditional(path, nd); |
| return ret; |
| } |
| |
| int follow_down_one(struct path *path) |
| { |
| struct vfsmount *mounted; |
| |
| mounted = lookup_mnt(path); |
| if (mounted) { |
| dput(path->dentry); |
| mntput(path->mnt); |
| path->mnt = mounted; |
| path->dentry = dget(mounted->mnt_root); |
| return 1; |
| } |
| return 0; |
| } |
| EXPORT_SYMBOL(follow_down_one); |
| |
| static inline int managed_dentry_rcu(const struct path *path) |
| { |
| return (path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) ? |
| path->dentry->d_op->d_manage(path, true) : 0; |
| } |
| |
| /* |
| * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if |
| * we meet a managed dentry that would need blocking. |
| */ |
| static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, |
| struct inode **inode, unsigned *seqp) |
| { |
| for (;;) { |
| struct mount *mounted; |
| /* |
| * Don't forget we might have a non-mountpoint managed dentry |
| * that wants to block transit. |
| */ |
| switch (managed_dentry_rcu(path)) { |
| case -ECHILD: |
| default: |
| return false; |
| case -EISDIR: |
| return true; |
| case 0: |
| break; |
| } |
| |
| if (!d_mountpoint(path->dentry)) |
| return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); |
| |
| mounted = __lookup_mnt(path->mnt, path->dentry); |
| if (!mounted) |
| break; |
| path->mnt = &mounted->mnt; |
| path->dentry = mounted->mnt.mnt_root; |
| nd->flags |= LOOKUP_JUMPED; |
| *seqp = read_seqcount_begin(&path->dentry->d_seq); |
| /* |
| * Update the inode too. We don't need to re-check the |
| * dentry sequence number here after this d_inode read, |
| * because a mount-point is always pinned. |
| */ |
| *inode = path->dentry->d_inode; |
| } |
| return !read_seqretry(&mount_lock, nd->m_seq) && |
| !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); |
| } |
| |
| static int follow_dotdot_rcu(struct nameidata *nd) |
| { |
| struct inode *inode = nd->inode; |
| |
| while (1) { |
| if (path_equal(&nd->path, &nd->root)) |
| break; |
| if (nd->path.dentry != nd->path.mnt->mnt_root) { |
| struct dentry *old = nd->path.dentry; |
| struct dentry *parent = old->d_parent; |
| unsigned seq; |
| |
| inode = parent->d_inode; |
| seq = read_seqcount_begin(&parent->d_seq); |
| if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq))) |
| return -ECHILD; |
| nd->path.dentry = parent; |
| nd->seq = seq; |
| if (unlikely(!path_connected(&nd->path))) |
| return -ENOENT; |
| break; |
| } else { |
| struct mount *mnt = real_mount(nd->path.mnt); |
| struct mount *mparent = mnt->mnt_parent; |
| struct dentry *mountpoint = mnt->mnt_mountpoint; |
| struct inode *inode2 = mountpoint->d_inode; |
| unsigned seq = read_seqcount_begin(&mountpoint->d_seq); |
| if (unlikely(read_seqretry(&mount_lock, nd->m_seq))) |
| return -ECHILD; |
| if (&mparent->mnt == nd->path.mnt) |
| break; |
| /* we know that mountpoint was pinned */ |
| nd->path.dentry = mountpoint; |
| nd->path.mnt = &mparent->mnt; |
| inode = inode2; |
| nd->seq = seq; |
| } |
| } |
| while (unlikely(d_mountpoint(nd->path.dentry))) { |
| struct mount *mounted; |
| mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry); |
| if (unlikely(read_seqretry(&mount_lock, nd->m_seq))) |
| return -ECHILD; |
| if (!mounted) |
| break; |
| nd->path.mnt = &mounted->mnt; |
| nd->path.dentry = mounted->mnt.mnt_root; |
| inode = nd->path.dentry->d_inode; |
| nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); |
| } |
| nd->inode = inode; |
| return 0; |
| } |
| |
| /* |
| * Follow down to the covering mount currently visible to userspace. At each |
| * point, the filesystem owning that dentry may be queried as to whether the |
| * caller is permitted to proceed or not. |
| */ |
| int follow_down(struct path *path) |
| { |
| unsigned managed; |
| int ret; |
| |
| while (managed = ACCESS_ONCE(path->dentry->d_flags), |
| unlikely(managed & DCACHE_MANAGED_DENTRY)) { |
| /* Allow the filesystem to manage the transit without i_mutex |
| * being held. |
| * |
| * We indicate to the filesystem if someone is trying to mount |
| * something here. This gives autofs the chance to deny anyone |
| * other than its daemon the right to mount on its |
| * superstructure. |
| * |
| * The filesystem may sleep at this point. |
| */ |
| if (managed & DCACHE_MANAGE_TRANSIT) { |
| BUG_ON(!path->dentry->d_op); |
| BUG_ON(!path->dentry->d_op->d_manage); |
| ret = path->dentry->d_op->d_manage(path, false); |
| if (ret < 0) |
| return ret == -EISDIR ? 0 : ret; |
| } |
| |
| /* Transit to a mounted filesystem. */ |
| if (managed & DCACHE_MOUNTED) { |
| struct vfsmount *mounted = lookup_mnt(path); |
| if (!mounted) |
| break; |
| dput(path->dentry); |
| mntput(path->mnt); |
| path->mnt = mounted; |
| path->dentry = dget(mounted->mnt_root); |
| continue; |
| } |
| |
| /* Don't handle automount points here */ |
| break; |
| } |
| return 0; |
| } |
| EXPORT_SYMBOL(follow_down); |
| |
| /* |
| * Skip to top of mountpoint pile in refwalk mode for follow_dotdot() |
| */ |
| static void follow_mount(struct path *path) |
| { |
| while (d_mountpoint(path->dentry)) { |
| struct vfsmount *mounted = lookup_mnt(path); |
| if (!mounted) |
| break; |
| dput(path->dentry); |
| mntput(path->mnt); |
| path->mnt = mounted; |
| path->dentry = dget(mounted->mnt_root); |
| } |
| } |
| |
| static int path_parent_directory(struct path *path) |
| { |
| struct dentry *old = path->dentry; |
| /* rare case of legitimate dget_parent()... */ |
| path->dentry = dget_parent(path->dentry); |
| dput(old); |
| if (unlikely(!path_connected(path))) |
| return -ENOENT; |
| return 0; |
| } |
| |
| static int follow_dotdot(struct nameidata *nd) |
| { |
| while(1) { |
| if (nd->path.dentry == nd->root.dentry && |
| nd->path.mnt == nd->root.mnt) { |
| break; |
| } |
| if (nd->path.dentry != nd->path.mnt->mnt_root) { |
| int ret = path_parent_directory(&nd->path); |
| if (ret) |
| return ret; |
| break; |
| } |
| if (!follow_up(&nd->path)) |
| break; |
| } |
| follow_mount(&nd->path); |
| nd->inode = nd->path.dentry->d_inode; |
| return 0; |
| } |
| |
| /* |
| * This looks up the name in dcache and possibly revalidates the found dentry. |
| * NULL is returned if the dentry does not exist in the cache. |
| */ |
| static struct dentry *lookup_dcache(const struct qstr *name, |
| struct dentry *dir, |
| unsigned int flags) |
| { |
| struct dentry *dentry = d_lookup(dir, name); |
| if (dentry) { |
| int error = d_revalidate(dentry, flags); |
| if (unlikely(error <= 0)) { |
| if (!error) |
| d_invalidate(dentry); |
| dput(dentry); |
| return ERR_PTR(error); |
| } |
| } |
| return dentry; |
| } |
| |
| /* |
| * Call i_op->lookup on the dentry. The dentry must be negative and |
| * unhashed. |
| * |
| * dir->d_inode->i_mutex must be held |
| */ |
| static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry, |
| unsigned int flags) |
| { |
| struct dentry *old; |
| |
| /* Don't create child dentry for a dead directory. */ |
| if (unlikely(IS_DEADDIR(dir))) { |
| dput(dentry); |
| return ERR_PTR(-ENOENT); |
| } |
| |
| old = dir->i_op->lookup(dir, dentry, flags); |
| if (unlikely(old)) { |
| dput(dentry); |
| dentry = old; |
| } |
| return dentry; |
| } |
| |
| static struct dentry *__lookup_hash(const struct qstr *name, |
| struct dentry *base, unsigned int flags) |
| { |
| struct dentry *dentry = lookup_dcache(name, base, flags); |
| |
| if (dentry) |
| return dentry; |
| |
| dentry = d_alloc(base, name); |
| if (unlikely(!dentry)) |
| return ERR_PTR(-ENOMEM); |
| |
| return lookup_real(base->d_inode, dentry, flags); |
| } |
| |
| static int lookup_fast(struct nameidata *nd, |
| struct path *path, struct inode **inode, |
| unsigned *seqp) |
| { |
| struct vfsmount *mnt = nd->path.mnt; |
| struct dentry *dentry, *parent = nd->path.dentry; |
| int status = 1; |
| int err; |
| |
| /* |
| * Rename seqlock is not required here because in the off chance |
| * of a false negative due to a concurrent rename, the caller is |
| * going to fall back to non-racy lookup. |
| */ |
| if (nd->flags & LOOKUP_RCU) { |
| unsigned seq; |
| bool negative; |
| dentry = __d_lookup_rcu(parent, &nd->last, &seq); |
| if (unlikely(!dentry)) { |
| if (unlazy_walk(nd)) |
| return -ECHILD; |
| return 0; |
| } |
| |
| /* |
| * This sequence count validates that the inode matches |
| * the dentry name information from lookup. |
| */ |
| *inode = d_backing_inode(dentry); |
| negative = d_is_negative(dentry); |
| if (unlikely(read_seqcount_retry(&dentry->d_seq, seq))) |
| return -ECHILD; |
| |
| /* |
| * This sequence count validates that the parent had no |
| * changes while we did the lookup of the dentry above. |
| * |
| * The memory barrier in read_seqcount_begin of child is |
| * enough, we can use __read_seqcount_retry here. |
| */ |
| if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq))) |
| return -ECHILD; |
| |
| *seqp = seq; |
| status = d_revalidate(dentry, nd->flags); |
| if (likely(status > 0)) { |
| /* |
| * Note: do negative dentry check after revalidation in |
| * case that drops it. |
| */ |
| if (unlikely(negative)) |
| return -ENOENT; |
| path->mnt = mnt; |
| path->dentry = dentry; |
| if (likely(__follow_mount_rcu(nd, path, inode, seqp))) |
| return 1; |
| } |
| if (unlazy_child(nd, dentry, seq)) |
| return -ECHILD; |
| if (unlikely(status == -ECHILD)) |
| /* we'd been told to redo it in non-rcu mode */ |
| status = d_revalidate(dentry, nd->flags); |
| } else { |
| dentry = __d_lookup(parent, &nd->last); |
| if (unlikely(!dentry)) |
| return 0; |
| status = d_revalidate(dentry, nd->flags); |
| } |
| if (unlikely(status <= 0)) { |
| if (!status) |
| d_invalidate(dentry); |
| dput(dentry); |
| return status; |
| } |
| if (unlikely(d_is_negative(dentry))) { |
| dput(dentry); |
| return -ENOENT; |
| } |
| |
| path->mnt = mnt; |
| path->dentry = dentry; |
| err = follow_managed(path, nd); |
| if (likely(err > 0)) |
| *inode = d_backing_inode(path->dentry); |
| return err; |
| } |
| |
| /* Fast lookup failed, do it the slow way */ |
| static struct dentry *lookup_slow(const struct qstr *name, |
| struct dentry *dir, |
| unsigned int flags) |
| { |
| struct dentry *dentry = ERR_PTR(-ENOENT), *old; |
| struct inode *inode = dir->d_inode; |
| DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq); |
| |
| inode_lock_shared(inode); |
| /* Don't go there if it's already dead */ |
| if (unlikely(IS_DEADDIR(inode))) |
| goto out; |
| again: |
| dentry = d_alloc_parallel(dir, name, &wq); |
| if (IS_ERR(dentry)) |
| goto out; |
| if (unlikely(!d_in_lookup(dentry))) { |
| if (!(flags & LOOKUP_NO_REVAL)) { |
| int error = d_revalidate(dentry, flags); |
| if (unlikely(error <= 0)) { |
| if (!error) { |
| d_invalidate(dentry); |
| dput(dentry); |
| goto again; |
| } |
| dput(dentry); |
| dentry = ERR_PTR(error); |
| } |
| } |
| } else { |
| old = inode->i_op->lookup(inode, dentry, flags); |
| d_lookup_done(dentry); |
| if (unlikely(old)) { |
| dput(dentry); |
| dentry = old; |
| } |
| } |
| out: |
| inode_unlock_shared(inode); |
| return dentry; |
| } |
| |
| static inline int may_lookup(struct nameidata *nd) |
| { |
| if (nd->flags & LOOKUP_RCU) { |
| int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK); |
| if (err != -ECHILD) |
| return err; |
| if (unlazy_walk(nd)) |
| return -ECHILD; |
| } |
| return inode_permission(nd->inode, MAY_EXEC); |
| } |
| |
| static inline int handle_dots(struct nameidata *nd, int type) |
| { |
| if (type == LAST_DOTDOT) { |
| if (!nd->root.mnt) |
| set_root(nd); |
| if (nd->flags & LOOKUP_RCU) { |
| return follow_dotdot_rcu(nd); |
| } else |
| return follow_dotdot(nd); |
| } |
| return 0; |
| } |
| |
| static int pick_link(struct nameidata *nd, struct path *link, |
| struct inode *inode, unsigned seq) |
| { |
| int error; |
| struct saved *last; |
| if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) { |
| path_to_nameidata(link, nd); |
| return -ELOOP; |
| } |
| if (!(nd->flags & LOOKUP_RCU)) { |
| if (link->mnt == nd->path.mnt) |
| mntget(link->mnt); |
| } |
| error = nd_alloc_stack(nd); |
| if (unlikely(error)) { |
| if (error == -ECHILD) { |
| if (unlikely(!legitimize_path(nd, link, seq))) { |
| drop_links(nd); |
| nd->depth = 0; |
| nd->flags &= ~LOOKUP_RCU; |
| nd->path.mnt = NULL; |
| nd->path.dentry = NULL; |
| if (!(nd->flags & LOOKUP_ROOT)) |
| nd->root.mnt = NULL; |
| rcu_read_unlock(); |
| } else if (likely(unlazy_walk(nd)) == 0) |
| error = nd_alloc_stack(nd); |
| } |
| if (error) { |
| path_put(link); |
| return error; |
| } |
| } |
| |
| last = nd->stack + nd->depth++; |
| last->link = *link; |
| clear_delayed_call(&last->done); |
| nd->link_inode = inode; |
| last->seq = seq; |
| return 1; |
| } |
| |
| enum {WALK_FOLLOW = 1, WALK_MORE = 2}; |
| |
| /* |
| * Do we need to follow links? We _really_ want to be able |
| * to do this check without having to look at inode->i_op, |
| * so we keep a cache of "no, this doesn't need follow_link" |
| * for the common case. |
| */ |
| static inline int step_into(struct nameidata *nd, struct path *path, |
| int flags, struct inode *inode, unsigned seq) |
| { |
| if (!(flags & WALK_MORE) && nd->depth) |
| put_link(nd); |
| if (likely(!d_is_symlink(path->dentry)) || |
| !(flags & WALK_FOLLOW || nd->flags & LOOKUP_FOLLOW)) { |
| /* not a symlink or should not follow */ |
| path_to_nameidata(path, nd); |
| nd->inode = inode; |
| nd->seq = seq; |
| return 0; |
| } |
| /* make sure that d_is_symlink above matches inode */ |
| if (nd->flags & LOOKUP_RCU) { |
| if (read_seqcount_retry(&path->dentry->d_seq, seq)) |
| return -ECHILD; |
| } |
| return pick_link(nd, path, inode, seq); |
| } |
| |
| static int walk_component(struct nameidata *nd, int flags) |
| { |
| struct path path; |
| struct inode *inode; |
| unsigned seq; |
| int err; |
| /* |
| * "." and ".." are special - ".." especially so because it has |
| * to be able to know about the current root directory and |
| * parent relationships. |
| */ |
| if (unlikely(nd->last_type != LAST_NORM)) { |
| err = handle_dots(nd, nd->last_type); |
| if (!(flags & WALK_MORE) && nd->depth) |
| put_link(nd); |
| return err; |
| } |
| err = lookup_fast(nd, &path, &inode, &seq); |
| if (unlikely(err <= 0)) { |
| if (err < 0) |
| return err; |
| path.dentry = lookup_slow(&nd->last, nd->path.dentry, |
| nd->flags); |
| if (IS_ERR(path.dentry)) |
| return PTR_ERR(path.dentry); |
| |
| path.mnt = nd->path.mnt; |
| err = follow_managed(&path, nd); |
| if (unlikely(err < 0)) |
| return err; |
| |
| if (unlikely(d_is_negative(path.dentry))) { |
| path_to_nameidata(&path, nd); |
| return -ENOENT; |
| } |
| |
| seq = 0; /* we are already out of RCU mode */ |
| inode = d_backing_inode(path.dentry); |
| } |
| |
| return step_into(nd, &path, flags, inode, seq); |
| } |
| |
| /* |
| * We can do the critical dentry name comparison and hashing |
| * operations one word at a time, but we are limited to: |
| * |
| * - Architectures with fast unaligned word accesses. We could |
| * do a "get_unaligned()" if this helps and is sufficiently |
| * fast. |
| * |
| * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we |
| * do not trap on the (extremely unlikely) case of a page |
| * crossing operation. |
| * |
| * - Furthermore, we need an efficient 64-bit compile for the |
| * 64-bit case in order to generate the "number of bytes in |
| * the final mask". Again, that could be replaced with a |
| * efficient population count instruction or similar. |
| */ |
| #ifdef CONFIG_DCACHE_WORD_ACCESS |
| |
| #include <asm/word-at-a-time.h> |
| |
| #ifdef HASH_MIX |
| |
| /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */ |
| |
| #elif defined(CONFIG_64BIT) |
| /* |
| * Register pressure in the mixing function is an issue, particularly |
| * on 32-bit x86, but almost any function requires one state value and |
| * one temporary. Instead, use a function designed for two state values |
| * and no temporaries. |
| * |
| * This function cannot create a collision in only two iterations, so |
| * we have two iterations to achieve avalanche. In those two iterations, |
| * we have six layers of mixing, which is enough to spread one bit's |
| * influence out to 2^6 = 64 state bits. |
| * |
| * Rotate constants are scored by considering either 64 one-bit input |
| * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the |
| * probability of that delta causing a change to each of the 128 output |
| * bits, using a sample of random initial states. |
| * |
| * The Shannon entropy of the computed probabilities is then summed |
| * to produce a score. Ideally, any input change has a 50% chance of |
| * toggling any given output bit. |
| * |
| * Mixing scores (in bits) for (12,45): |
| * Input delta: 1-bit 2-bit |
| * 1 round: 713.3 42542.6 |
| * 2 rounds: 2753.7 140389.8 |
| * 3 rounds: 5954.1 233458.2 |
| * 4 rounds: 7862.6 256672.2 |
| * Perfect: 8192 258048 |
| * (64*128) (64*63/2 * 128) |
| */ |
| #define HASH_MIX(x, y, a) \ |
| ( x ^= (a), \ |
| y ^= x, x = rol64(x,12),\ |
| x += y, y = rol64(y,45),\ |
| y *= 9 ) |
| |
| /* |
| * Fold two longs into one 32-bit hash value. This must be fast, but |
| * latency isn't quite as critical, as there is a fair bit of additional |
| * work done before the hash value is used. |
| */ |
| static inline unsigned int fold_hash(unsigned long x, unsigned long y) |
| { |
| y ^= x * GOLDEN_RATIO_64; |
| y *= GOLDEN_RATIO_64; |
| return y >> 32; |
| } |
| |
| #else /* 32-bit case */ |
| |
| /* |
| * Mixing scores (in bits) for (7,20): |
| * Input delta: 1-bit 2-bit |
| * 1 round: 330.3 9201.6 |
| * 2 rounds: 1246.4 25475.4 |
| * 3 rounds: 1907.1 31295.1 |
| * 4 rounds: 2042.3 31718.6 |
| * Perfect: 2048 31744 |
| * (32*64) (32*31/2 * 64) |
| */ |
| #define HASH_MIX(x, y, a) \ |
| ( x ^= (a), \ |
| y ^= x, x = rol32(x, 7),\ |
| x += y, y = rol32(y,20),\ |
| y *= 9 ) |
| |
| static inline unsigned int fold_hash(unsigned long x, unsigned long y) |
| { |
| /* Use arch-optimized multiply if one exists */ |
| return __hash_32(y ^ __hash_32(x)); |
| } |
| |
| #endif |
| |
| /* |
| * Return the hash of a string of known length. This is carfully |
| * designed to match hash_name(), which is the more critical function. |
| * In particular, we must end by hashing a final word containing 0..7 |
| * payload bytes, to match the way that hash_name() iterates until it |
| * finds the delimiter after the name. |
| */ |
| unsigned int full_name_hash(const void *salt, const char *name, unsigned int len) |
| { |
| unsigned long a, x = 0, y = (unsigned long)salt; |
| |
| for (;;) { |
| if (!len) |
| goto done; |
| a = load_unaligned_zeropad(name); |
| if (len < sizeof(unsigned long)) |
| break; |
| HASH_MIX(x, y, a); |
| name += sizeof(unsigned long); |
| len -= sizeof(unsigned long); |
| } |
| x ^= a & bytemask_from_count(len); |
| done: |
| return fold_hash(x, y); |
| } |
| EXPORT_SYMBOL(full_name_hash); |
| |
| /* Return the "hash_len" (hash and length) of a null-terminated string */ |
| u64 hashlen_string(const void *salt, const char *name) |
| { |
| unsigned long a = 0, x = 0, y = (unsigned long)salt; |
| unsigned long adata, mask, len; |
| const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; |
| |
| len = 0; |
| goto inside; |
| |
| do { |
| HASH_MIX(x, y, a); |
| len += sizeof(unsigned long); |
| inside: |
| a = load_unaligned_zeropad(name+len); |
| } while (!has_zero(a, &adata, &constants)); |
| |
| adata = prep_zero_mask(a, adata, &constants); |
| mask = create_zero_mask(adata); |
| x ^= a & zero_bytemask(mask); |
| |
| return hashlen_create(fold_hash(x, y), len + find_zero(mask)); |
| } |
| EXPORT_SYMBOL(hashlen_string); |
| |
| /* |
| * Calculate the length and hash of the path component, and |
| * return the "hash_len" as the result. |
| */ |
| static inline u64 hash_name(const void *salt, const char *name) |
| { |
| unsigned long a = 0, b, x = 0, y = (unsigned long)salt; |
| unsigned long adata, bdata, mask, len; |
| const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; |
| |
| len = 0; |
| goto inside; |
| |
| do { |
| HASH_MIX(x, y, a); |
| len += sizeof(unsigned long); |
| inside: |
| a = load_unaligned_zeropad(name+len); |
| b = a ^ REPEAT_BYTE('/'); |
| } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants))); |
| |
| adata = prep_zero_mask(a, adata, &constants); |
| bdata = prep_zero_mask(b, bdata, &constants); |
| mask = create_zero_mask(adata | bdata); |
| x ^= a & zero_bytemask(mask); |
| |
| return hashlen_create(fold_hash(x, y), len + find_zero(mask)); |
| } |
| |
| #else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */ |
| |
| /* Return the hash of a string of known length */ |
| unsigned int full_name_hash(const void *salt, const char *name, unsigned int len) |
| { |
| unsigned long hash = init_name_hash(salt); |
| while (len--) |
| hash = partial_name_hash((unsigned char)*name++, hash); |
| return end_name_hash(hash); |
| } |
| EXPORT_SYMBOL(full_name_hash); |
| |
| /* Return the "hash_len" (hash and length) of a null-terminated string */ |
| u64 hashlen_string(const void *salt, const char *name) |
| { |
| unsigned long hash = init_name_hash(salt); |
| unsigned long len = 0, c; |
| |
| c = (unsigned char)*name; |
| while (c) { |
| len++; |
| hash = partial_name_hash(c, hash); |
| c = (unsigned char)name[len]; |
| } |
| return hashlen_create(end_name_hash(hash), len); |
| } |
| EXPORT_SYMBOL(hashlen_string); |
| |
| /* |
| * We know there's a real path component here of at least |
| * one character. |
| */ |
| static inline u64 hash_name(const void *salt, const char *name) |
| { |
| unsigned long hash = init_name_hash(salt); |
| unsigned long len = 0, c; |
| |
| c = (unsigned char)*name; |
| do { |
| len++; |
| hash = partial_name_hash(c, hash); |
| c = (unsigned char)name[len]; |
| } while (c && c != '/'); |
| return hashlen_create(end_name_hash(hash), len); |
| } |
| |
| #endif |
| |
| /* |
| * Name resolution. |
| * This is the basic name resolution function, turning a pathname into |
| * the final dentry. We expect 'base' to be positive and a directory. |
| * |
| * Returns 0 and nd will have valid dentry and mnt on success. |
| * Returns error and drops reference to input namei data on failure. |
| */ |
| static int link_path_walk(const char *name, struct nameidata *nd) |
| { |
| int err; |
| |
| while (*name=='/') |
| name++; |
| if (!*name) |
| return 0; |
| |
| /* At this point we know we have a real path component. */ |
| for(;;) { |
| u64 hash_len; |
| int type; |
| |
| err = may_lookup(nd); |
| if (err) |
| return err; |
| |
| hash_len = hash_name(nd->path.dentry, name); |
| |
| type = LAST_NORM; |
| if (name[0] == '.') switch (hashlen_len(hash_len)) { |
| case 2: |
| if (name[1] == '.') { |
| type = LAST_DOTDOT; |
| nd->flags |= LOOKUP_JUMPED; |
| } |
| break; |
| case 1: |
| type = LAST_DOT; |
| } |
| if (likely(type == LAST_NORM)) { |
| struct dentry *parent = nd->path.dentry; |
| nd->flags &= ~LOOKUP_JUMPED; |
| if (unlikely(parent->d_flags & DCACHE_OP_HASH)) { |
| struct qstr this = { { .hash_len = hash_len }, .name = name }; |
| err = parent->d_op->d_hash(parent, &this); |
| if (err < 0) |
| return err; |
| hash_len = this.hash_len; |
| name = this.name; |
| } |
| } |
| |
| nd->last.hash_len = hash_len; |
| nd->last.name = name; |
| nd->last_type = type; |
| |
| name += hashlen_len(hash_len); |
| if (!*name) |
| goto OK; |
| /* |
| * If it wasn't NUL, we know it was '/'. Skip that |
| * slash, and continue until no more slashes. |
| */ |
| do { |
| name++; |
| } while (unlikely(*name == '/')); |
| if (unlikely(!*name)) { |
| OK: |
| /* pathname body, done */ |
| if (!nd->depth) |
| return 0; |
| name = nd->stack[nd->depth - 1].name; |
| /* trailing symlink, done */ |
| if (!name) |
| return 0; |
| /* last component of nested symlink */ |
| err = walk_component(nd, WALK_FOLLOW); |
| } else { |
| /* not the last component */ |
| err = walk_component(nd, WALK_FOLLOW | WALK_MORE); |
| } |
| if (err < 0) |
| return err; |
| |
| if (err) { |
| const char *s = get_link(nd); |
| |
| if (IS_ERR(s)) |
| return PTR_ERR(s); |
| err = 0; |
| if (unlikely(!s)) { |
| /* jumped */ |
| put_link(nd); |
| } else { |
| nd->stack[nd->depth - 1].name = name; |
| name = s; |
| continue; |
| } |
| } |
| if (unlikely(!d_can_lookup(nd->path.dentry))) { |
| if (nd->flags & LOOKUP_RCU) { |
| if (unlazy_walk(nd)) |
| return -ECHILD; |
| } |
| return -ENOTDIR; |
| } |
| } |
| } |
| |
| static const char *path_init(struct nameidata *nd, unsigned flags) |
| { |
| const char *s = nd->name->name; |
| |
| if (!*s) |
| flags &= ~LOOKUP_RCU; |
| |
| nd->last_type = LAST_ROOT; /* if there are only slashes... */ |
| nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT; |
| nd->depth = 0; |
| if (flags & LOOKUP_ROOT) { |
| struct dentry *root = nd->root.dentry; |
| struct inode *inode = root->d_inode; |
| if (*s && unlikely(!d_can_lookup(root))) |
| return ERR_PTR(-ENOTDIR); |
| nd->path = nd->root; |
| nd->inode = inode; |
| if (flags & LOOKUP_RCU) { |
| rcu_read_lock(); |
| nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); |
| nd->root_seq = nd->seq; |
| nd->m_seq = read_seqbegin(&mount_lock); |
| } else { |
| path_get(&nd->path); |
| } |
| return s; |
| } |
| |
| nd->root.mnt = NULL; |
| nd->path.mnt = NULL; |
| nd->path.dentry = NULL; |
| |
| nd->m_seq = read_seqbegin(&mount_lock); |
| if (*s == '/') { |
| if (flags & LOOKUP_RCU) |
| rcu_read_lock(); |
| set_root(nd); |
| if (likely(!nd_jump_root(nd))) |
| return s; |
| nd->root.mnt = NULL; |
| rcu_read_unlock(); |
| return ERR_PTR(-ECHILD); |
| } else if (nd->dfd == AT_FDCWD) { |
| if (flags & LOOKUP_RCU) { |
| struct fs_struct *fs = current->fs; |
| unsigned seq; |
| |
| rcu_read_lock(); |
| |
| do { |
| seq = read_seqcount_begin(&fs->seq); |
| nd->path = fs->pwd; |
| nd->inode = nd->path.dentry->d_inode; |
| nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); |
| } while (read_seqcount_retry(&fs->seq, seq)); |
| } else { |
| get_fs_pwd(current->fs, &nd->path); |
| nd->inode = nd->path.dentry->d_inode; |
| } |
| return s; |
| } else { |
| /* Caller must check execute permissions on the starting path component */ |
| struct fd f = fdget_raw(nd->dfd); |
| struct dentry *dentry; |
| |
| if (!f.file) |
| return ERR_PTR(-EBADF); |
| |
| dentry = f.file->f_path.dentry; |
| |
| if (*s) { |
| if (!d_can_lookup(dentry)) { |
| fdput(f); |
| return ERR_PTR(-ENOTDIR); |
| } |
| } |
| |
| nd->path = f.file->f_path; |
| if (flags & LOOKUP_RCU) { |
| rcu_read_lock(); |
| nd->inode = nd->path.dentry->d_inode; |
| nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); |
| } else { |
| path_get(&nd->path); |
| nd->inode = nd->path.dentry->d_inode; |
| } |
| fdput(f); |
| return s; |
| } |
| } |
| |
| static const char *trailing_symlink(struct nameidata *nd) |
| { |
| const char *s; |
| int error = may_follow_link(nd); |
| if (unlikely(error)) |
| return ERR_PTR(error); |
| nd->flags |= LOOKUP_PARENT; |
| nd->stack[0].name = NULL; |
| s = get_link(nd); |
| return s ? s : ""; |
| } |
| |
| static inline int lookup_last(struct nameidata *nd) |
| { |
| if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) |
| nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; |
| |
| nd->flags &= ~LOOKUP_PARENT; |
| return walk_component(nd, 0); |
| } |
| |
| static int handle_lookup_down(struct nameidata *nd) |
| { |
| struct path path = nd->path; |
| struct inode *inode = nd->inode; |
| unsigned seq = nd->seq; |
| int err; |
| |
| if (nd->flags & LOOKUP_RCU) { |
| /* |
| * don't bother with unlazy_walk on failure - we are |
| * at the very beginning of walk, so we lose nothing |
| * if we simply redo everything in non-RCU mode |
| */ |
| if (unlikely(!__follow_mount_rcu(nd, &path, &inode, &seq))) |
| return -ECHILD; |
| } else { |
| dget(path.dentry); |
| err = follow_managed(&path, nd); |
| if (unlikely(err < 0)) |
| return err; |
| inode = d_backing_inode(path.dentry); |
| seq = 0; |
| } |
| path_to_nameidata(&path, nd); |
| nd->inode = inode; |
| nd->seq = seq; |
| return 0; |
| } |
| |
| /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ |
| static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path) |
| { |
| const char *s = path_init(nd, flags); |
| int err; |
| |
| if (IS_ERR(s)) |
| return PTR_ERR(s); |
| |
| if (unlikely(flags & LOOKUP_DOWN)) { |
| err = handle_lookup_down(nd); |
| if (unlikely(err < 0)) { |
| terminate_walk(nd); |
| return err; |
| } |
| } |
| |
| while (!(err = link_path_walk(s, nd)) |
| && ((err = lookup_last(nd)) > 0)) { |
| s = trailing_symlink(nd); |
| if (IS_ERR(s)) { |
| err = PTR_ERR(s); |
| break; |
| } |
| } |
| if (!err) |
| err = complete_walk(nd); |
| |
| if (!err && nd->flags & LOOKUP_DIRECTORY) |
| if (!d_can_lookup(nd->path.dentry)) |
| err = -ENOTDIR; |
| if (!err) { |
| *path = nd->path; |
| nd->path.mnt = NULL; |
| nd->path.dentry = NULL; |
| } |
| terminate_walk(nd); |
| return err; |
| } |
| |
| static int filename_lookup(int dfd, struct filename *name, unsigned flags, |
| struct path *path, struct path *root) |
| { |
| int retval; |
| struct nameidata nd; |
| if (IS_ERR(name)) |
| return PTR_ERR(name); |
| if (unlikely(root)) { |
| nd.root = *root; |
| flags |= LOOKUP_ROOT; |
| } |
| set_nameidata(&nd, dfd, name); |
| retval = path_lookupat(&nd, flags | LOOKUP_RCU, path); |
| if (unlikely(retval == -ECHILD)) |
| retval = path_lookupat(&nd, flags, path); |
| if (unlikely(retval == -ESTALE)) |
| retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path); |
| |
| if (likely(!retval)) |
| audit_inode(name, path->dentry, flags & LOOKUP_PARENT); |
| restore_nameidata(); |
| putname(name); |
| return retval; |
| } |
| |
| /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ |
| static int path_parentat(struct nameidata *nd, unsigned flags, |
| struct path *parent) |
| { |
| const char *s = path_init(nd, flags); |
| int err; |
| if (IS_ERR(s)) |
| return PTR_ERR(s); |
| err = link_path_walk(s, nd); |
| if (!err) |
| err = complete_walk(nd); |
| if (!err) { |
| *parent = nd->path; |
| nd->path.mnt = NULL; |
| nd->path.dentry = NULL; |
| } |
| terminate_walk(nd); |
| return err; |
| } |
| |
| static struct filename *filename_parentat(int dfd, struct filename *name, |
| unsigned int flags, struct path *parent, |
| struct qstr *last, int *type) |
| { |
| int retval; |
| struct nameidata nd; |
| |
| if (IS_ERR(name)) |
| return name; |
| set_nameidata(&nd, dfd, name); |
| retval = path_parentat(&nd, flags | LOOKUP_RCU, parent); |
| if (unlikely(retval == -ECHILD)) |
| retval = path_parentat(&nd, flags, parent); |
| if (unlikely(retval == -ESTALE)) |
| retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent); |
| if (likely(!retval)) { |
| *last = nd.last; |
| *type = nd.last_type; |
| audit_inode(name, parent->dentry, LOOKUP_PARENT); |
| } else { |
| putname(name); |
| name = ERR_PTR(retval); |
| } |
| restore_nameidata(); |
| return name; |
| } |
| |
| /* does lookup, returns the object with parent locked */ |
| struct dentry *kern_path_locked(const char *name, struct path *path) |
| { |
| struct filename *filename; |
| struct dentry *d; |
| struct qstr last; |
| int type; |
| |
| filename = filename_parentat(AT_FDCWD, getname_kernel(name), 0, path, |
| &last, &type); |
| if (IS_ERR(filename)) |
| return ERR_CAST(filename); |
| if (unlikely(type != LAST_NORM)) { |
| path_put(path); |
| putname(filename); |
| return ERR_PTR(-EINVAL); |
| } |
| inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); |
| d = __lookup_hash(&last, path->dentry, 0); |
| if (IS_ERR(d)) { |
| inode_unlock(path->dentry->d_inode); |
| path_put(path); |
| } |
| putname(filename); |
| return d; |
| } |
| |
| int kern_path(const char *name, unsigned int flags, struct path *path) |
| { |
| return filename_lookup(AT_FDCWD, getname_kernel(name), |
| flags, path, NULL); |
| } |
| EXPORT_SYMBOL(kern_path); |
| |
| /** |
| * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair |
| * @dentry: pointer to dentry of the base directory |
| * @mnt: pointer to vfs mount of the base directory |
| * @name: pointer to file name |
| * @flags: lookup flags |
| * @path: pointer to struct path to fill |
| */ |
| int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, |
| const char *name, unsigned int flags, |
| struct path *path) |
| { |
| struct path root = {.mnt = mnt, .dentry = dentry}; |
| /* the first argument of filename_lookup() is ignored with root */ |
| return filename_lookup(AT_FDCWD, getname_kernel(name), |
| flags , path, &root); |
| } |
| EXPORT_SYMBOL(vfs_path_lookup); |
| |
| /** |
| * lookup_one_len - filesystem helper to lookup single pathname component |
| * @name: pathname component to lookup |
| * @base: base directory to lookup from |
| * @len: maximum length @len should be interpreted to |
| * |
| * Note that this routine is purely a helper for filesystem usage and should |
| * not be called by generic code. |
| * |
| * The caller must hold base->i_mutex. |
| */ |
| struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) |
| { |
| struct qstr this; |
| unsigned int c; |
| int err; |
| |
| WARN_ON_ONCE(!inode_is_locked(base->d_inode)); |
| |
| this.name = name; |
| this.len = len; |
| this.hash = full_name_hash(base, name, len); |
| if (!len) |
| return ERR_PTR(-EACCES); |
| |
| if (unlikely(name[0] == '.')) { |
| if (len < 2 || (len == 2 && name[1] == '.')) |
| return ERR_PTR(-EACCES); |
| } |
| |
| while (len--) { |
| c = *(const unsigned char *)name++; |
| if (c == '/' || c == '\0') |
| return ERR_PTR(-EACCES); |
| } |
| /* |
| * See if the low-level filesystem might want |
| * to use its own hash.. |
| */ |
| if (base->d_flags & DCACHE_OP_HASH) { |
| int err = base->d_op->d_hash(base, &this); |
| if (err < 0) |
| return ERR_PTR(err); |
| } |
| |
| err = inode_permission(base->d_inode, MAY_EXEC); |
| if (err) |
| return ERR_PTR(err); |
| |
| return __lookup_hash(&this, base, 0); |
| } |
| EXPORT_SYMBOL(lookup_one_len); |
| |
| /** |
| * lookup_one_len_unlocked - filesystem helper to lookup single pathname component |
| * @name: pathname component to lookup |
| * @base: base directory to lookup from |
| * @len: maximum length @len should be interpreted to |
| * |
| * Note that this routine is purely a helper for filesystem usage and should |
| * not be called by generic code. |
| * |
| * Unlike lookup_one_len, it should be called without the parent |
| * i_mutex held, and will take the i_mutex itself if necessary. |
| */ |
| struct dentry *lookup_one_len_unlocked(const char *name, |
| struct dentry *base, int len) |
| { |
| struct qstr this; |
| unsigned int c; |
| int err; |
| struct dentry *ret; |
| |
| this.name = name; |
| this.len = len; |
| this.hash = full_name_hash(base, name, len); |
| if (!len) |
| return ERR_PTR(-EACCES); |
| |
| if (unlikely(name[0] == '.')) { |
| if (len < 2 || (len == 2 && name[1] == '.')) |
| return ERR_PTR(-EACCES); |
| } |
| |
| while (len--) { |
| c = *(const unsigned char *)name++; |
| if (c == '/' || c == '\0') |
| return ERR_PTR(-EACCES); |
| } |
| /* |
| * See if the low-level filesystem might want |
| * to use its own hash.. |
| */ |
| if (base->d_flags & DCACHE_OP_HASH) { |
| int err = base->d_op->d_hash(base, &this); |
| if (err < 0) |
| return ERR_PTR(err); |
| } |
| |
| err = inode_permission(base->d_inode, MAY_EXEC); |
| if (err) |
| return ERR_PTR(err); |
| |
| ret = lookup_dcache(&this, base, 0); |
| if (!ret) |
| ret = lookup_slow(&this, base, 0); |
| return ret; |
| } |
| EXPORT_SYMBOL(lookup_one_len_unlocked); |
| |
| #ifdef CONFIG_UNIX98_PTYS |
| int path_pts(struct path *path) |
| { |
| /* Find something mounted on "pts" in the same directory as |
| * the input path. |
| */ |
| struct dentry *child, *parent; |
| struct qstr this; |
| int ret; |
| |
| ret = path_parent_directory(path); |
| if (ret) |
| return ret; |
| |
| parent = path->dentry; |
| this.name = "pts"; |
| this.len = 3; |
| child = d_hash_and_lookup(parent, &this); |
| if (!child) |
| return -ENOENT; |
| |
| path->dentry = child; |
| dput(parent); |
| follow_mount(path); |
| return 0; |
| } |
| #endif |
| |
| int user_path_at_empty(int dfd, const char __user *name, unsigned flags, |
| struct path *path, int *empty) |
| { |
| return filename_lookup(dfd, getname_flags(name, flags, empty), |
| flags, path, NULL); |
| } |
| EXPORT_SYMBOL(user_path_at_empty); |
| |
| /** |
| * mountpoint_last - look up last component for umount |
| * @nd: pathwalk nameidata - currently pointing at parent directory of "last" |
| * |
| * This is a special lookup_last function just for umount. In this case, we |
| * need to resolve the path without doing any revalidation. |
| * |
| * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since |
| * mountpoints are always pinned in the dcache, their ancestors are too. Thus, |
| * in almost all cases, this lookup will be served out of the dcache. The only |
| * cases where it won't are if nd->last refers to a symlink or the path is |
| * bogus and it doesn't exist. |
| * |
| * Returns: |
| * -error: if there was an error during lookup. This includes -ENOENT if the |
| * lookup found a negative dentry. |
| * |
| * 0: if we successfully resolved nd->last and found it to not to be a |
| * symlink that needs to be followed. |
| * |
| * 1: if we successfully resolved nd->last and found it to be a symlink |
| * that needs to be followed. |
| */ |
| static int |
| mountpoint_last(struct nameidata *nd) |
| { |
| int error = 0; |
| struct dentry *dir = nd->path.dentry; |
| struct path path; |
| |
| /* If we're in rcuwalk, drop out of it to handle last component */ |
| if (nd->flags & LOOKUP_RCU) { |
| if (unlazy_walk(nd)) |
| return -ECHILD; |
| } |
| |
| nd->flags &= ~LOOKUP_PARENT; |
| |
| if (unlikely(nd->last_type != LAST_NORM)) { |
| error = handle_dots(nd, nd->last_type); |
| if (error) |
| return error; |
| path.dentry = dget(nd->path.dentry); |
| } else { |
| path.dentry = d_lookup(dir, &nd->last); |
| if (!path.dentry) { |
| /* |
| * No cached dentry. Mounted dentries are pinned in the |
| * cache, so that means that this dentry is probably |
| * a symlink or the path doesn't actually point |
| * to a mounted dentry. |
| */ |
| path.dentry = lookup_slow(&nd->last, dir, |
| nd->flags | LOOKUP_NO_REVAL); |
| if (IS_ERR(path.dentry)) |
| return PTR_ERR(path.dentry); |
| } |
| } |
| if (d_is_negative(path.dentry)) { |
| dput(path.dentry); |
| return -ENOENT; |
| } |
| path.mnt = nd->path.mnt; |
| return step_into(nd, &path, 0, d_backing_inode(path.dentry), 0); |
| } |
| |
| /** |
| * path_mountpoint - look up a path to be umounted |
| * @nd: lookup context |
| * @flags: lookup flags |
| * @path: pointer to container for result |
| * |
| * Look up the given name, but don't attempt to revalidate the last component. |
| * Returns 0 and "path" will be valid on success; Returns error otherwise. |
| */ |
| static int |
| path_mountpoint(struct nameidata *nd, unsigned flags, struct path *path) |
| { |
| const char *s = path_init(nd, flags); |
| int err; |
| if (IS_ERR(s)) |
| return PTR_ERR(s); |
| while (!(err = link_path_walk(s, nd)) && |
| (err = mountpoint_last(nd)) > 0) { |
| s = trailing_symlink(nd); |
| if (IS_ERR(s)) { |
| err = PTR_ERR(s); |
| break; |
| } |
| } |
| if (!err) { |
| *path = nd->path; |
| nd->path.mnt = NULL; |
| nd->path.dentry = NULL; |
| follow_mount(path); |
| } |
| terminate_walk(nd); |
| return err; |
| } |
| |
| static int |
| filename_mountpoint(int dfd, struct filename *name, struct path *path, |
| unsigned int flags) |
| { |
| struct nameidata nd; |
| int error; |
| if (IS_ERR(name)) |
| return PTR_ERR(name); |
| set_nameidata(&nd, dfd, name); |
| error = path_mountpoint(&nd, flags | LOOKUP_RCU, path); |
| if (unlikely(error == -ECHILD)) |
| error = path_mountpoint(&nd, flags, path); |
| if (unlikely(error == -ESTALE)) |
| error = path_mountpoint(&nd, flags | LOOKUP_REVAL, path); |
| if (likely(!error)) |
| audit_inode(name, path->dentry, 0); |
| restore_nameidata(); |
| putname(name); |
| return error; |
| } |
| |
| /** |
| * user_path_mountpoint_at - lookup a path from userland in order to umount it |
| * @dfd: directory file descriptor |
| * @name: pathname from userland |
| * @flags: lookup flags |
| * @path: pointer to container to hold result |
| * |
| * A umount is a special case for path walking. We're not actually interested |
| * in the inode in this situation, and ESTALE errors can be a problem. We |
| * simply want track down the dentry and vfsmount attached at the mountpoint |
| * and avoid revalidating the last component. |
| * |
| * Returns 0 and populates "path" on success. |
| */ |
| int |
| user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags, |
| struct path *path) |
| { |
| return filename_mountpoint(dfd, getname(name), path, flags); |
| } |
| |
| int |
| kern_path_mountpoint(int dfd, const char *name, struct path *path, |
| unsigned int flags) |
| { |
| return filename_mountpoint(dfd, getname_kernel(name), path, flags); |
| } |
| EXPORT_SYMBOL(kern_path_mountpoint); |
| |
| int __check_sticky(struct inode *dir, struct inode *inode) |
| { |
| kuid_t fsuid = current_fsuid(); |
| |
| if (uid_eq(inode->i_uid, fsuid)) |
| return 0; |
| if (uid_eq(dir->i_uid, fsuid)) |
| return 0; |
| return !capable_wrt_inode_uidgid(inode, CAP_FOWNER); |
| } |
| EXPORT_SYMBOL(__check_sticky); |
| |
| /* |
| * Check whether we can remove a link victim from directory dir, check |
| * whether the type of victim is right. |
| * 1. We can't do it if dir is read-only (done in permission()) |
| * 2. We should have write and exec permissions on dir |
| * 3. We can't remove anything from append-only dir |
| * 4. We can't do anything with immutable dir (done in permission()) |
| * 5. If the sticky bit on dir is set we should either |
| * a. be owner of dir, or |
| * b. be owner of victim, or |
| * c. have CAP_FOWNER capability |
| * 6. If the victim is append-only or immutable we can't do antyhing with |
| * links pointing to it. |
| * 7. If the victim has an unknown uid or gid we can't change the inode. |
| * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR. |
| * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR. |
| * 10. We can't remove a root or mountpoint. |
| * 11. We don't allow removal of NFS sillyrenamed files; it's handled by |
| * nfs_async_unlink(). |
| */ |
| static int may_delete(struct inode *dir, struct dentry *victim, bool isdir) |
| { |
| struct inode *inode = d_backing_inode(victim); |
| int error; |
| |
| if (d_is_negative(victim)) |
| return -ENOENT; |
| BUG_ON(!inode); |
| |
| BUG_ON(victim->d_parent->d_inode != dir); |
| audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE); |
| |
| error = inode_permission(dir, MAY_WRITE | MAY_EXEC); |
| if (error) |
| return error; |
| if (IS_APPEND(dir)) |
| return -EPERM; |
| |
| if (check_sticky(dir, inode) || IS_APPEND(inode) || |
| IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || HAS_UNMAPPED_ID(inode)) |
| return -EPERM; |
| if (isdir) { |
| if (!d_is_dir(victim)) |
| return -ENOTDIR; |
| if (IS_ROOT(victim)) |
| return -EBUSY; |
| } else if (d_is_dir(victim)) |
| return -EISDIR; |
| if (IS_DEADDIR(dir)) |
| return -ENOENT; |
| if (victim->d_flags & DCACHE_NFSFS_RENAMED) |
| return -EBUSY; |
| return 0; |
| } |
| |
| /* Check whether we can create an object with dentry child in directory |
| * dir. |
| * 1. We can't do it if child already exists (open has special treatment for |
| * this case, but since we are inlined it's OK) |
| * 2. We can't do it if dir is read-only (done in permission()) |
| * 3. We can't do it if the fs can't represent the fsuid or fsgid. |
| * 4. We should have write and exec permissions on dir |
| * 5. We can't do it if dir is immutable (done in permission()) |
| */ |
| static inline int may_create(struct inode *dir, struct dentry *child) |
| { |
| struct user_namespace *s_user_ns; |
| audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE); |
| if (child->d_inode) |
| return -EEXIST; |
| if (IS_DEADDIR(dir)) |
| return -ENOENT; |
| s_user_ns = dir->i_sb->s_user_ns; |
| if (!kuid_has_mapping(s_user_ns, current_fsuid()) || |
| !kgid_has_mapping(s_user_ns, current_fsgid())) |
| return -EOVERFLOW; |
| return inode_permission(dir, MAY_WRITE | MAY_EXEC); |
| } |
| |
| /* |
| * p1 and p2 should be directories on the same fs. |
| */ |
| struct dentry *lock_rename(struct dentry *p1, struct dentry *p2) |
| { |
| struct dentry *p; |
| |
| if (p1 == p2) { |
| inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); |
| return NULL; |
| } |
| |
| mutex_lock(&p1->d_sb->s_vfs_rename_mutex); |
| |
| p = d_ancestor(p2, p1); |
| if (p) { |
| inode_lock_nested(p2->d_inode, I_MUTEX_PARENT); |
| inode_lock_nested(p1->d_inode, I_MUTEX_CHILD); |
| return p; |
| } |
| |
| p = d_ancestor(p1, p2); |
| if (p) { |
| inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); |
| inode_lock_nested(p2->d_inode, I_MUTEX_CHILD); |
| return p; |
| } |
| |
| inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); |
| inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2); |
| return NULL; |
| } |
| EXPORT_SYMBOL(lock_rename); |
| |
| void unlock_rename(struct dentry *p1, struct dentry *p2) |
| { |
| inode_unlock(p1->d_inode); |
| if (p1 != p2) { |
| inode_unlock(p2->d_inode); |
| mutex_unlock(&p1->d_sb->s_vfs_rename_mutex); |
| } |
| } |
| EXPORT_SYMBOL(unlock_rename); |
| |
| int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, |
| bool want_excl) |
| { |
| int error = may_create(dir, dentry); |
| if (error) |
| return error; |
| |
| if (!dir->i_op->create) |
| return -EACCES; /* shouldn't it be ENOSYS? */ |
| mode &= S_IALLUGO; |
| mode |= S_IFREG; |
| error = security_inode_create(dir, dentry, mode); |
| if (error) |
| return error; |
| error = dir->i_op->create(dir, dentry, mode, want_excl); |
| if (!error) |
| fsnotify_create(dir, dentry); |
| return error; |
| } |
| EXPORT_SYMBOL(vfs_create); |
| |
| bool may_open_dev(const struct path *path) |
| { |
| return !(path->mnt->mnt_flags & MNT_NODEV) && |
| !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV); |
| } |
| |
| static int may_open(const struct path *path, int acc_mode, int flag) |
| { |
| struct dentry *dentry = path->dentry; |
| struct inode *inode = dentry->d_inode; |
| int error; |
| |
| if (!inode) |
| return -ENOENT; |
| |
| switch (inode->i_mode & S_IFMT) { |
| case S_IFLNK: |
| return -ELOOP; |
| case S_IFDIR: |
| if (acc_mode & MAY_WRITE) |
| return -EISDIR; |
| break; |
| case S_IFBLK: |
| case S_IFCHR: |
| if (!may_open_dev(path)) |
| return -EACCES; |
| /*FALLTHRU*/ |
| case S_IFIFO: |
| case S_IFSOCK: |
| flag &= ~O_TRUNC; |
| break; |
| } |
| |
| error = inode_permission(inode, MAY_OPEN | acc_mode); |
| if (error) |
| return error; |
| |
| /* |
| * An append-only file must be opened in append mode for writing. |
| */ |
| if (IS_APPEND(inode)) { |
| if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) |
| return -EPERM; |
| if (flag & O_TRUNC) |
| return -EPERM; |
| } |
| |
| /* O_NOATIME can only be set by the owner or superuser */ |
| if (flag & O_NOATIME && !inode_owner_or_capable(inode)) |
| return -EPERM; |
| |
| return 0; |
| } |
| |
| static int handle_truncate(struct file *filp) |
| { |
| const struct path *path = &filp->f_path; |
| struct inode *inode = path->dentry->d_inode; |
| int error = get_write_access(inode); |
| if (error) |
| return error; |
| /* |
| * Refuse to truncate files with mandatory locks held on them. |
| */ |
| error = locks_verify_locked(filp); |
| if (!error) |
| error = security_path_truncate(path); |
| if (!error) { |
| error = do_truncate(path->dentry, 0, |
| ATTR_MTIME|ATTR_CTIME|ATTR_OPEN, |
| filp); |
| } |
| put_write_access(inode); |
| return error; |
| } |
| |
| static inline int open_to_namei_flags(int flag) |
| { |
| if ((flag & O_ACCMODE) == 3) |
| flag--; |
| return flag; |
| } |
| |
| static int may_o_create(const struct path *dir, struct dentry *dentry, umode_t mode) |
| { |
| struct user_namespace *s_user_ns; |
| int error = security_path_mknod(dir, dentry, mode, 0); |
| if (error) |
| return error; |
| |
| s_user_ns = dir->dentry->d_sb->s_user_ns; |
| if (!kuid_has_mapping(s_user_ns, current_fsuid()) || |
| !kgid_has_mapping(s_user_ns, current_fsgid())) |
| return -EOVERFLOW; |
| |
| error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC); |
| if (error) |
| return error; |
| |
| return security_inode_create(dir->dentry->d_inode, dentry, mode); |
| } |
| |
| /* |
| * Attempt to atomically look up, create and open a file from a negative |
| * dentry. |
| * |
| * Returns 0 if successful. The file will have been created and attached to |
| * @file by the filesystem calling finish_open(). |
| * |
| * Returns 1 if the file was looked up only or didn't need creating. The |
| * caller will need to perform the open themselves. @path will have been |
| * updated to point to the new dentry. This may be negative. |
| * |
| * Returns an error code otherwise. |
| */ |
| static int atomic_open(struct nameidata *nd, struct dentry *dentry, |
| struct path *path, struct file *file, |
| const struct open_flags *op, |
| int open_flag, umode_t mode, |
| int *opened) |
| { |
| struct dentry *const DENTRY_NOT_SET = (void *) -1UL; |
| struct inode *dir = nd->path.dentry->d_inode; |
| int error; |
| |
| if (!(~open_flag & (O_EXCL | O_CREAT))) /* both O_EXCL and O_CREAT */ |
| open_flag &= ~O_TRUNC; |
| |
| if (nd->flags & LOOKUP_DIRECTORY) |
| open_flag |= O_DIRECTORY; |
| |
| file->f_path.dentry = DENTRY_NOT_SET; |
| file->f_path.mnt = nd->path.mnt; |
| error = dir->i_op->atomic_open(dir, dentry, file, |
| open_to_namei_flags(open_flag), |
| mode, opened); |
| d_lookup_done(dentry); |
| if (!error) { |
| /* |
| * We didn't have the inode before the open, so check open |
| * permission here. |
| */ |
| int acc_mode = op->acc_mode; |
| if (*opened & FILE_CREATED) { |
| WARN_ON(!(open_flag & O_CREAT)); |
| fsnotify_create(dir, dentry); |
| acc_mode = 0; |
| } |
| error = may_open(&file->f_path, acc_mode, open_flag); |
| if (WARN_ON(error > 0)) |
| error = -EINVAL; |
| } else if (error > 0) { |
| if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) { |
| error = -EIO; |
| } else { |
| if (file->f_path.dentry) { |
| dput(dentry); |
| dentry = file->f_path.dentry; |
| } |
| if (*opened & FILE_CREATED) |
| fsnotify_create(dir, dentry); |
| if (unlikely(d_is_negative(dentry))) { |
| error = -ENOENT; |
| } else { |
| path->dentry = dentry; |
| path->mnt = nd->path.mnt; |
| return 1; |
| } |
| } |
| } |
| dput(dentry); |
| return error; |
| } |
| |
| /* |
| * Look up and maybe create and open the last component. |
| * |
| * Must be called with i_mutex held on parent. |
| * |
| * Returns 0 if the file was successfully atomically created (if necessary) and |
| * opened. In this case the file will be returned attached to @file. |
| * |
| * Returns 1 if the file was not completely opened at this time, though lookups |
|