linux-kernel - Re: [PATCH 1/2 v2] ipc,sem: fix use after free on IPC_RMID after a task using same semaphore set exits

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Message-ID: <55CA3F33.9090205@colorfullife.com>
Date:	Tue, 11 Aug 2015 20:30:11 +0200
From:	Manfred Spraul <manfred@...orfullife.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Herton R. Krzesinski" <herton@...hat.com>,
	linux-kernel@...r.kernel.org, Davidlohr Bueso <dave@...olabs.net>,
	Rafael Aquini <aquini@...hat.com>,
	Joe Perches <joe@...ches.com>,
	Aristeu Rozanski <aris@...hat.com>, djeffery@...hat.com
Subject: Re: [PATCH 1/2 v2] ipc,sem: fix use after free on IPC_RMID after a
 task using same semaphore set exits

On 08/11/2015 07:19 PM, Herton R. Krzesinski wrote:
> The current semaphore code allows a potential use after free: in exit_sem we may
> free the task's sem_undo_list while there is still another task looping through
> the same semaphore set and cleaning the sem_undo list at freeary function (the
> task called IPC_RMID for the same semaphore set).
>
> For example, with a test program [1] running which keeps forking a lot of processes
> (which then do a semop call with SEM_UNDO flag), and with the parent right after
> removing the semaphore set with IPC_RMID, and a kernel built with CONFIG_SLAB,
> CONFIG_SLAB_DEBUG and CONFIG_DEBUG_SPINLOCK, you can easily see something like
> the following in the kernel log:
>
>
> Signed-off-by: Herton R. Krzesinski <herton@...hat.com>
> Cc: stable@...r.kernel.org
Acked-by: Manfred Spraul <manfred@...orfullife.com>

--
     Manfred
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