linux-kernel - Re: [PATCH] proc: fix null pointer deref in proc_pid

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Message-ID: <20120111204330.GT2618@outflux.net>
Date:	Wed, 11 Jan 2012 12:43:30 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Xiaotian Feng <xtfeng@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Xiaotian Feng <dannyfeng@...cent.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vasiliy Kulikov <segoon@...nwall.com>,
	Stephen Wilson <wilsons@...rt.ca>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH] proc: fix null pointer deref in proc_pid_permission()

Hi,

On Wed, Jan 11, 2012 at 01:47:05PM -0500, 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.

Nice catch!

However since this error is returned to userspace, shouldn't this be
-ENOENT instead?

-Kees

-- 
Kees Cook
ChromeOS Security
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