Re: [PATCH] proc: fix null pointer deref in proc_pid_permission()

[David Rientjes]

On Wed, 11 Jan 2012, Xiaotian Feng wrote:

> get_proc_task() can fail to search the task and return NULL, put_task_struct()
> will then bomb the kernel with following oops:
> 
> [ 1870.574045] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
> [ 1870.574065] IP: [<ffffffff81217d34>] proc_pid_permission+0x64/0xe0
> [ 1870.574088] PGD 112075067 PUD 112814067 PMD 0
> [ 1870.574106] Oops: 0002 [#1] PREEMPT SMP
> 
> This is a regression introduced by commit 0499680a, kernel should
> return -ESRCH if get_proc_task() failed.
> 
> Signed-off-by: Xiaotian Feng <dannyfeng@xxxxxxxxxxx>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Vasiliy Kulikov <segoon@xxxxxxxxxxxx>
> Cc: Stephen Wilson <wilsons@xxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>

Acked-by: David Rientjes <rientjes@xxxxxxxxxx>

You're right to use -ESRCH so it matches the same behavior as the 
remainder of /proc/pid when get_proc_task() returns NULL.
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