linux-kernel - Re: [PATCH] drm/i915: Fix refcount leak and possible NULL pointer dereference.

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Message-ID: <20131225215249.GA3832@nuc-i3427.alporthouse.com>
Date:	Wed, 25 Dec 2013 21:52:49 +0000
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	ben@...dawsk.net, daniel.vetter@...ll.ch,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/i915: Fix refcount leak and possible NULL pointer
 dereference.

On Tue, Dec 24, 2013 at 08:50:23PM +0900, Tetsuo Handa wrote:
> >From 482be6384379072eb4c0d45d0ab8a25df4f59ed7 Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Date: Tue, 24 Dec 2013 18:04:14 +0900
> Subject: [PATCH] drm/i915: Fix refcount leak and possible NULL pointer dereference.
> 
> Since get_pid_task() grabs a reference on the task_struct, we have to drop the
> refcount after reading that task's comm name. Also, directly reading like
> get_pid_task()->comm can trigger an oops when get_pid_task() returned NULL.

The second issue is moot as file itself cannot exist if the task_struct
is NULL, and the task_struct cannot be destroyed until we finish the
function. The simpler fix would appear to be s/get_pid_task/pid_task/
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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