linux-kernel - Re: [PATCH] posix-timer: don't call idr

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Message-ID: <512540E6.7070302@oracle.com>
Date:	Wed, 20 Feb 2013 16:32:22 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Tejun Heo <tj@...nel.org>
CC:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] posix-timer: don't call idr_find() w/ negative ID

On 02/20/2013 04:01 PM, Tejun Heo wrote:
> Recent idr updates make idr_find() trigger WARN_ON_ONCE() before
> returning NULL when a negative ID is specified.  Apparently,
> posix-timer::__lock_timer() was depending on idr_find() returning NULL
> on negative ID, thus triggering the new WARN_ON_ONCE().  Make
> __lock_timer() first check whether @timer_id is negative and return
> NULL without invoking idr_find() if so.
> 
> Note that the previous code was theoretically broken.  idr_find()
> masked off the sign bit before performing lookup and if the matching
> IDs were in use, it would have returned pointer for the incorrect
> entry.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Reported-by: Sasha Levin <sasha.levin@...cle.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> ---
> Sasha, can you please test whether this makes the warning go away?

Looks like it did.


Thanks,
Sasha
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