linux-kernel - Re: [PATCH] [ipc/sem.c] fix race with concurrent semtimedop() timeouts and IPC

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Message-Id: <20110720235836.c40ec351.akpm@linux-foundation.org>
Date:	Wed, 20 Jul 2011 23:58:36 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Manfred Spraul <manfred@...orfullife.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Yuriy Yevtukhov <yuriy@...z.com>
Subject: Re: [PATCH] [ipc/sem.c] fix race with concurrent semtimedop()
 timeouts and IPC_RMID

On Thu, 21 Jul 2011 08:42:53 +0200 Manfred Spraul <manfred@...orfullife.com> wrote:

> If a semaphore array is removed and in parallel a sleeping task is woken up
> (signal or timeout, does not matter), then the woken up task does not wait
> until wake_up_sem_queue_do() is completed. This will cause crashes, because
> wake_up_sem_queue_do() will read from a stale pointer.
> 
> The fix is simple: Regardless of anything, always call get_queue_result().
> This function waits until wake_up_sem_queue_do() has finished it's task.
> 
> Andrew, could you please take care of merging the patch?

yup, thanks for this.  It's good to hear from you, and that you've
still got what it takes :)

Do you know how long this bug has been around for?  Somewhere between
2.6.32 and 2.6.36, but that a large interval!
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