itimer: Schedule silent NULL pointer fixup in setitimer() for removal

setitimer() should return -EFAULT if called with an invalid pointer
for value. The current code excludes a NULL pointer from this rule and
silently uses it to stop the timer. This violates the spec.

Warn about user space apps which rely on that feature and schedule it
for removal.

[ tglx: Massaged changelog, warn message and Doc entry ]

Signed-off-by: Sasikantha babu <sasikanth.v19@gmail.com>
Link: http://lkml.kernel.org/r/1332340854-26053-1-git-send-email-sasikanth.v19@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 4 insertions, 1 deletions

diff --git a/kernel/itimer.c b/kernel/itimer.c
index 22000c3db0d..c70369a74b5 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -284,8 +284,11 @@ SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
         if (value) {
                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
                         return -EFAULT;
-        } else
+        } else {
                 memset((char *) &set_buffer, 0, sizeof(set_buffer));
+                WARN_ONCE(1, "setitimer: new_value pointer is NULL."
+                          " Misfeature support will be removed\n");
+        }
 
         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
         if (error || !ovalue)