sysctl: deprecate sys_sysctl in a user space visible fashion.
After adding checking to register_sysctl_table and finding a whole new set
of bugs. Missed by countless code reviews and testers I have finally lost
patience with the binary sysctl interface.
The binary sysctl interface has been sort of deprecated for years and
finding a user space program that uses the syscall is more difficult then
finding a needle in a haystack. Problems continue to crop up, with the in
kernel implementation. So since supporting something that no one uses is
silly, deprecate sys_sysctl with a sufficient grace period and notice that
the handful of user space applications that care can be fixed or replaced.
The /proc/sys sysctl interface that people use will continue to be
supported indefinitely.
This patch moves the tested warning about sysctls from the path where
sys_sysctl to a separate path called from both implementations of
sys_sysctl, and it adds a proper entry into
Documentation/feature-removal-schedule.
Allowing us to revisit this in a couple years time and actually kill
sys_sysctl.
[lethal@linux-sh.org: sysctl: Fix syscall disabled build]
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 280ec06..5b25162 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -82,6 +82,41 @@
---------------------------
+What: sys_sysctl
+When: September 2010
+Option: CONFIG_SYSCTL_SYSCALL
+Why: The same information is available in a more convenient from
+ /proc/sys, and none of the sysctl variables appear to be
+ important performance wise.
+
+ Binary sysctls are a long standing source of subtle kernel
+ bugs and security issues.
+
+ When I looked several months ago all I could find after
+ searching several distributions were 5 user space programs and
+ glibc (which falls back to /proc/sys) using this syscall.
+
+ The man page for sysctl(2) documents it as unusable for user
+ space programs.
+
+ sysctl(2) is not generally ABI compatible to a 32bit user
+ space application on a 64bit and a 32bit kernel.
+
+ For the last several months the policy has been no new binary
+ sysctls and no one has put forward an argument to use them.
+
+ Binary sysctls issues seem to keep happening appearing so
+ properly deprecating them (with a warning to user space) and a
+ 2 year grace warning period will mean eventually we can kill
+ them and end the pain.
+
+ In the mean time individual binary sysctls can be dealt with
+ in a piecewise fashion.
+
+Who: Eric Biederman <ebiederm@xmission.com>
+
+---------------------------
+
What: a.out interpreter support for ELF executables
When: 2.6.25
Files: fs/binfmt_elf.c
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 62e53a0..c25e67e 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -55,6 +55,8 @@
#include <asm/stacktrace.h>
#endif
+static int deprecated_sysctl_warning(struct __sysctl_args *args);
+
#if defined(CONFIG_SYSCTL)
/* External variables not in a header file. */
@@ -1347,10 +1349,15 @@
if (copy_from_user(&tmp, args, sizeof(tmp)))
return -EFAULT;
+ error = deprecated_sysctl_warning(&tmp);
+ if (error)
+ goto out;
+
lock_kernel();
error = do_sysctl(tmp.name, tmp.nlen, tmp.oldval, tmp.oldlenp,
tmp.newval, tmp.newlen);
unlock_kernel();
+out:
return error;
}
#endif /* CONFIG_SYSCTL_SYSCALL */
@@ -2540,35 +2547,19 @@
asmlinkage long sys_sysctl(struct __sysctl_args __user *args)
{
- static int msg_count;
struct __sysctl_args tmp;
- int name[CTL_MAXNAME];
- int i;
+ int error;
- /* Read in the sysctl name for better debug message logging */
if (copy_from_user(&tmp, args, sizeof(tmp)))
return -EFAULT;
- if (tmp.nlen <= 0 || tmp.nlen >= CTL_MAXNAME)
- return -ENOTDIR;
- for (i = 0; i < tmp.nlen; i++)
- if (get_user(name[i], tmp.name + i))
- return -EFAULT;
- /* Ignore accesses to kernel.version */
- if ((tmp.nlen == 2) && (name[0] == CTL_KERN) && (name[1] == KERN_VERSION))
- goto out;
+ error = deprecated_sysctl_warning(&tmp);
- if (msg_count < 5) {
- msg_count++;
- printk(KERN_INFO
- "warning: process `%s' used the removed sysctl "
- "system call with ", current->comm);
- for (i = 0; i < tmp.nlen; i++)
- printk("%d.", name[i]);
- printk("\n");
- }
-out:
- return -ENOSYS;
+ /* If no error reading the parameters then just -ENOSYS ... */
+ if (!error)
+ error = -ENOSYS;
+
+ return error;
}
int sysctl_data(struct ctl_table *table, int __user *name, int nlen,
@@ -2608,6 +2599,33 @@
#endif /* CONFIG_SYSCTL_SYSCALL */
+static int deprecated_sysctl_warning(struct __sysctl_args *args)
+{
+ static int msg_count;
+ int name[CTL_MAXNAME];
+ int i;
+
+ /* Read in the sysctl name for better debug message logging */
+ for (i = 0; i < args->nlen; i++)
+ if (get_user(name[i], args->name + i))
+ return -EFAULT;
+
+ /* Ignore accesses to kernel.version */
+ if ((args->nlen == 2) && (name[0] == CTL_KERN) && (name[1] == KERN_VERSION))
+ return 0;
+
+ if (msg_count < 5) {
+ msg_count++;
+ printk(KERN_INFO
+ "warning: process `%s' used the deprecated sysctl "
+ "system call with ", current->comm);
+ for (i = 0; i < args->nlen; i++)
+ printk("%d.", name[i]);
+ printk("\n");
+ }
+ return 0;
+}
+
/*
* No sense putting this after each symbol definition, twice,
* exception granted :-)
