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To: Daniel Axtens <dja@axtens.net>, linuxppc-dev@ozlabs.org
From: Michael Ellerman <mpe@ellerman.id.au>
Cc: mikey@neuling.org, Daniel Axtens <dja@axtens.net>, imunsie@au.ibm.com
Subject: Re: cxl: Check if afu is not null in cxl_slbia
Message-Id: <20150710065506.72FE41402D6@ozlabs.org>
Date: Fri, 10 Jul 2015 16:55:06 +1000 (AEST)
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On Thu, 2015-09-07 at 23:04:25 UTC, Daniel Axtens wrote:
> The pointer to an AFU in the adapter's list of AFUs can be null
> if we're in the process of removing AFUs. The afu_list_lock
> doesn't guard against this.
> 
> Say we have 2 slices, and we're in the process of removing cxl.
>  - We remove the AFUs in order (see cxl_remove). In cxl_remove_afu
>    for AFU 0, we take the lock, set adapter->afu[0] = NULL, and
>    release the lock.
>  - Then we get an slbia. In cxl_slbia we take the lock, and set
>    afu = adapter->afu[0], which is NULL.
>  - Therefore our attempt to check afu->enabled will blow up.
> 
> Therefore, check if afu is a null pointer before dereferencing it.
>
Cc: stable@vger.kernel.org
> Signed-off-by: Daniel Axtens <dja@axtens.net>
> Acked-by: Michael Neuling <mikey@neuling.org>
> Acked-by: Ian Munsie <imunsie@au1.ibm.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/2c069a118fe1d80c47dc

cheers