fs/notify/fanotify/fanotify.c - arm/linux-arm64-legacy - Git at Google

 #include <linux/fanotify.h>
 #include <linux/fdtable.h>
 #include <linux/fsnotify_backend.h>
 #include <linux/init.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h> /* UINT_MAX */
 #include <linux/mount.h>
 #include <linux/sched.h>
 #include <linux/types.h>
 #include <linux/wait.h>

 #include "fanotify.h"

 static bool should_merge(struct fsnotify_event *old_fsn,
 			 struct fsnotify_event *new_fsn)
 {
 	struct fanotify_event_info *old, *new;

 	pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn);
 	old = FANOTIFY_E(old_fsn);
 	new = FANOTIFY_E(new_fsn);

 	if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid &&
 	    old->path.mnt == new->path.mnt &&
 	    old->path.dentry == new->path.dentry)
 		return true;
 	return false;
 }

 /* and the list better be locked by something too! */
 static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
 {
 	struct fsnotify_event *test_event;
 	bool do_merge = false;

 	pr_debug("%s: list=%p event=%p\n", __func__, list, event);

 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 	/*
 	 * Don't merge a permission event with any other event so that we know
 	 * the event structure we have created in fanotify_handle_event() is the
 	 * one we should check for permission response.
 	 */
 	if (event->mask & FAN_ALL_PERM_EVENTS)
 		return 0;
 #endif

 	list_for_each_entry_reverse(test_event, list, list) {
 		if (should_merge(test_event, event)) {
 			do_merge = true;
 			break;
 		}
 	}

 	if (!do_merge)
 		return 0;

 	test_event->mask |= event->mask;
 	return 1;
 }

 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 static int fanotify_get_response(struct fsnotify_group *group,
 				 struct fanotify_perm_event_info *event)
 {
 	int ret;

 	pr_debug("%s: group=%p event=%p\n", __func__, group, event);

 	wait_event(group->fanotify_data.access_waitq, event->response ||
 				atomic_read(&group->fanotify_data.bypass_perm));

 	if (!event->response) /* bypass_perm set */
 		return 0;

 	/* userspace responded, convert to something usable */
 	switch (event->response) {
 	case FAN_ALLOW:
 		ret = 0;
 		break;
 	case FAN_DENY:
 	default:
 		ret = -EPERM;
 	}
 	event->response = 0;

 	pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
 		 group, event, ret);

 	return ret;
 }
 #endif

 static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark,
 				       struct fsnotify_mark *vfsmnt_mark,
 				       u32 event_mask,
 				       void *data, int data_type)
 {
 	__u32 marks_mask, marks_ignored_mask;
 	struct path *path = data;

 	pr_debug("%s: inode_mark=%p vfsmnt_mark=%p mask=%x data=%p"
 		 " data_type=%d\n", __func__, inode_mark, vfsmnt_mark,
 		 event_mask, data, data_type);

 	/* if we don't have enough info to send an event to userspace say no */
 	if (data_type != FSNOTIFY_EVENT_PATH)
 		return false;

 	/* sorry, fanotify only gives a damn about files and dirs */
 	if (!S_ISREG(path->dentry->d_inode->i_mode) &&
 	    !S_ISDIR(path->dentry->d_inode->i_mode))
 		return false;

 	if (inode_mark && vfsmnt_mark) {
 		marks_mask = (vfsmnt_mark->mask | inode_mark->mask);
 		marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask);
 	} else if (inode_mark) {
 		/*
 		 * if the event is for a child and this inode doesn't care about
 		 * events on the child, don't send it!
 		 */
 		if ((event_mask & FS_EVENT_ON_CHILD) &&
 		    !(inode_mark->mask & FS_EVENT_ON_CHILD))
 			return false;
 		marks_mask = inode_mark->mask;
 		marks_ignored_mask = inode_mark->ignored_mask;
 	} else if (vfsmnt_mark) {
 		marks_mask = vfsmnt_mark->mask;
 		marks_ignored_mask = vfsmnt_mark->ignored_mask;
 	} else {
 		BUG();
 	}

 	if (S_ISDIR(path->dentry->d_inode->i_mode) &&
 	    (marks_ignored_mask & FS_ISDIR))
 		return false;

 	if (event_mask & marks_mask & ~marks_ignored_mask)
 		return true;

 	return false;
 }

 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask,
 						 struct path *path)
 {
 	struct fanotify_event_info *event;

 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 	if (mask & FAN_ALL_PERM_EVENTS) {
 		struct fanotify_perm_event_info *pevent;

 		pevent = kmem_cache_alloc(fanotify_perm_event_cachep,
 					  GFP_KERNEL);
 		if (!pevent)
 			return NULL;
 		event = &pevent->fae;
 		pevent->response = 0;
 		goto init;
 	}
 #endif
 	event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
 	if (!event)
 		return NULL;
 init: __maybe_unused
 	fsnotify_init_event(&event->fse, inode, mask);
 	event->tgid = get_pid(task_tgid(current));
 	if (path) {
 		event->path = *path;
 		path_get(&event->path);
 	} else {
 		event->path.mnt = NULL;
 		event->path.dentry = NULL;
 	}
 	return event;
 }

 static int fanotify_handle_event(struct fsnotify_group *group,
 				 struct inode *inode,
 				 struct fsnotify_mark *inode_mark,
 				 struct fsnotify_mark *fanotify_mark,
 				 u32 mask, void *data, int data_type,
 				 const unsigned char *file_name, u32 cookie)
 {
 	int ret = 0;
 	struct fanotify_event_info *event;
 	struct fsnotify_event *fsn_event;

 	BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
 	BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
 	BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
 	BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
 	BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
 	BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
 	BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
 	BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
 	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 	BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);

 	if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data,
 					data_type))
 		return 0;

 	pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
 		 mask);

 	event = fanotify_alloc_event(inode, mask, data);
 	if (unlikely(!event))
 		return -ENOMEM;

 	fsn_event = &event->fse;
 	ret = fsnotify_add_notify_event(group, fsn_event, fanotify_merge);
 	if (ret) {
 		/* Permission events shouldn't be merged */
 		BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS);
 		/* Our event wasn't used in the end. Free it. */
 		fsnotify_destroy_event(group, fsn_event);

 		return 0;
 	}

 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 	if (mask & FAN_ALL_PERM_EVENTS) {
 		ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event));
 		fsnotify_destroy_event(group, fsn_event);
 	}
 #endif
 	return ret;
 }

 static void fanotify_free_group_priv(struct fsnotify_group *group)
 {
 	struct user_struct *user;

 	user = group->fanotify_data.user;
 	atomic_dec(&user->fanotify_listeners);
 	free_uid(user);
 }

 static void fanotify_free_event(struct fsnotify_event *fsn_event)
 {
 	struct fanotify_event_info *event;

 	event = FANOTIFY_E(fsn_event);
 	path_put(&event->path);
 	put_pid(event->tgid);
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 	if (fsn_event->mask & FAN_ALL_PERM_EVENTS) {
 		kmem_cache_free(fanotify_perm_event_cachep,
 				FANOTIFY_PE(fsn_event));
 		return;
 	}
 #endif
 	kmem_cache_free(fanotify_event_cachep, event);
 }

 const struct fsnotify_ops fanotify_fsnotify_ops = {
 	.handle_event = fanotify_handle_event,
 	.free_group_priv = fanotify_free_group_priv,
 	.free_event = fanotify_free_event,
 };
	#include <linux/fanotify.h>
	#include <linux/fdtable.h>
	#include <linux/fsnotify_backend.h>
	#include <linux/init.h>
	#include <linux/jiffies.h>
	#include <linux/kernel.h> /* UINT_MAX */
	#include <linux/mount.h>
	#include <linux/sched.h>
	#include <linux/types.h>
	#include <linux/wait.h>

	#include "fanotify.h"

	static bool should_merge(struct fsnotify_event *old_fsn,
	struct fsnotify_event *new_fsn)
	{
	struct fanotify_event_info old, new;

	pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn);
	old = FANOTIFY_E(old_fsn);
	new = FANOTIFY_E(new_fsn);

	if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid &&
	old->path.mnt == new->path.mnt &&
	old->path.dentry == new->path.dentry)
	return true;
	return false;
	}

	/* and the list better be locked by something too! */
	static int fanotify_merge(struct list_head list, struct fsnotify_event event)
	{
	struct fsnotify_event *test_event;
	bool do_merge = false;

	pr_debug("%s: list=%p event=%p\n", __func__, list, event);

	#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
	/*
	* Don't merge a permission event with any other event so that we know
	* the event structure we have created in fanotify_handle_event() is the
	* one we should check for permission response.
	*/
	if (event->mask & FAN_ALL_PERM_EVENTS)
	return 0;
	#endif

	list_for_each_entry_reverse(test_event, list, list) {
	if (should_merge(test_event, event)) {
	do_merge = true;
	break;
	}
	}

	if (!do_merge)
	return 0;

	test_event->mask \|= event->mask;
	return 1;
	}

	#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
	static int fanotify_get_response(struct fsnotify_group *group,
	struct fanotify_perm_event_info *event)
	{
	int ret;

	pr_debug("%s: group=%p event=%p\n", __func__, group, event);

	wait_event(group->fanotify_data.access_waitq, event->response \|\|
	atomic_read(&group->fanotify_data.bypass_perm));

	if (!event->response) /* bypass_perm set */
	return 0;

	/* userspace responded, convert to something usable */
	switch (event->response) {
	case FAN_ALLOW:
	ret = 0;
	break;
	case FAN_DENY:
	default:
	ret = -EPERM;
	}
	event->response = 0;

	pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
	group, event, ret);

	return ret;
	}
	#endif

	static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark,
	struct fsnotify_mark *vfsmnt_mark,
	u32 event_mask,
	void *data, int data_type)
	{
	__u32 marks_mask, marks_ignored_mask;
	struct path *path = data;

	pr_debug("%s: inode_mark=%p vfsmnt_mark=%p mask=%x data=%p"
	" data_type=%d\n", __func__, inode_mark, vfsmnt_mark,
	event_mask, data, data_type);

	/* if we don't have enough info to send an event to userspace say no */
	if (data_type != FSNOTIFY_EVENT_PATH)
	return false;

	/* sorry, fanotify only gives a damn about files and dirs */
	if (!S_ISREG(path->dentry->d_inode->i_mode) &&
	!S_ISDIR(path->dentry->d_inode->i_mode))
	return false;

	if (inode_mark && vfsmnt_mark) {
	marks_mask = (vfsmnt_mark->mask \| inode_mark->mask);
	marks_ignored_mask = (vfsmnt_mark->ignored_mask \| inode_mark->ignored_mask);
	} else if (inode_mark) {
	/*
	* if the event is for a child and this inode doesn't care about
	* events on the child, don't send it!
	*/
	if ((event_mask & FS_EVENT_ON_CHILD) &&
	!(inode_mark->mask & FS_EVENT_ON_CHILD))
	return false;
	marks_mask = inode_mark->mask;
	marks_ignored_mask = inode_mark->ignored_mask;
	} else if (vfsmnt_mark) {
	marks_mask = vfsmnt_mark->mask;
	marks_ignored_mask = vfsmnt_mark->ignored_mask;
	} else {
	BUG();
	}

	if (S_ISDIR(path->dentry->d_inode->i_mode) &&
	(marks_ignored_mask & FS_ISDIR))
	return false;

	if (event_mask & marks_mask & ~marks_ignored_mask)
	return true;

	return false;
	}

	struct fanotify_event_info fanotify_alloc_event(struct inode inode, u32 mask,
	struct path *path)
	{
	struct fanotify_event_info *event;

	#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
	if (mask & FAN_ALL_PERM_EVENTS) {
	struct fanotify_perm_event_info *pevent;

	pevent = kmem_cache_alloc(fanotify_perm_event_cachep,
	GFP_KERNEL);
	if (!pevent)
	return NULL;
	event = &pevent->fae;
	pevent->response = 0;
	goto init;
	}
	#endif
	event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
	if (!event)
	return NULL;
	init: __maybe_unused
	fsnotify_init_event(&event->fse, inode, mask);
	event->tgid = get_pid(task_tgid(current));
	if (path) {
	event->path = *path;
	path_get(&event->path);
	} else {
	event->path.mnt = NULL;
	event->path.dentry = NULL;
	}
	return event;
	}

	static int fanotify_handle_event(struct fsnotify_group *group,
	struct inode *inode,
	struct fsnotify_mark *inode_mark,
	struct fsnotify_mark *fanotify_mark,
	u32 mask, void *data, int data_type,
	const unsigned char *file_name, u32 cookie)
	{
	int ret = 0;
	struct fanotify_event_info *event;
	struct fsnotify_event *fsn_event;

	BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
	BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
	BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
	BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
	BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
	BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
	BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
	BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
	BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);

	if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data,
	data_type))
	return 0;

	pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
	mask);

	event = fanotify_alloc_event(inode, mask, data);
	if (unlikely(!event))
	return -ENOMEM;

	fsn_event = &event->fse;
	ret = fsnotify_add_notify_event(group, fsn_event, fanotify_merge);
	if (ret) {
	/* Permission events shouldn't be merged */
	BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS);
	/* Our event wasn't used in the end. Free it. */
	fsnotify_destroy_event(group, fsn_event);

	return 0;
	}

	#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
	if (mask & FAN_ALL_PERM_EVENTS) {
	ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event));
	fsnotify_destroy_event(group, fsn_event);
	}
	#endif
	return ret;
	}

	static void fanotify_free_group_priv(struct fsnotify_group *group)
	{
	struct user_struct *user;

	user = group->fanotify_data.user;
	atomic_dec(&user->fanotify_listeners);
	free_uid(user);
	}

	static void fanotify_free_event(struct fsnotify_event *fsn_event)
	{
	struct fanotify_event_info *event;

	event = FANOTIFY_E(fsn_event);
	path_put(&event->path);
	put_pid(event->tgid);
	#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
	if (fsn_event->mask & FAN_ALL_PERM_EVENTS) {
	kmem_cache_free(fanotify_perm_event_cachep,
	FANOTIFY_PE(fsn_event));
	return;
	}
	#endif
	kmem_cache_free(fanotify_event_cachep, event);
	}

	const struct fsnotify_ops fanotify_fsnotify_ops = {
	.handle_event = fanotify_handle_event,
	.free_group_priv = fanotify_free_group_priv,
	.free_event = fanotify_free_event,
	};