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Subject: Re: [PATCH] rapidio: fix rio_dma_transfer error handling
To:     Andrew Morton <akpm@linux-foundation.org>,
        Ioan Nicu <ioan.nicu.ext@nokia.com>
Cc:     Barry Wood <barry.wood@idt.com>,
        Matt Porter <mporter@kernel.crashing.org>,
        Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Logan Gunthorpe <logang@deltatee.com>,
        Chris Wilson <chris@chris-wilson.co.uk>,
        Tvrtko Ursulin <tvrtko.ursulin@intel.com>,
        Frank Kunz <frank.kunz@nokia.com>,
        Alexander Sverdlin <alexander.sverdlin@nokia.com>,
        linux-kernel@vger.kernel.org
References: <20180412150605.GA31409@nokia.com>
 <20180412142803.cd235a40155503700dc73b21@linux-foundation.org>
From:   Alexandre Bounine <alex.bou9@gmail.com>
Message-ID: <d77db0b1-2cca-c0f6-987d-32ffb45cb16f@gmail.com>
Date:   Thu, 12 Apr 2018 19:44:01 -0400
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On 2018-04-12 05:28 PM, Andrew Morton wrote:
> On Thu, 12 Apr 2018 17:06:05 +0200 Ioan Nicu <ioan.nicu.ext@nokia.com> wrote:
> 
>> Some of the mport_dma_req structure members were initialized late
>> inside the do_dma_request() function, just before submitting the
>> request to the dma engine. But we have some error branches before
>> that. In case of such an error, the code would return on the error
>> path and trigger the calling of dma_req_free() with a req structure
>> which is not completely initialized. This causes a NULL pointer
>> dereference in dma_req_free().
>>
>> This patch fixes these error branches by making sure that all
>> necessary mport_dma_req structure members are initialized in
>> rio_dma_transfer() immediately after the request structure gets
>> allocated.
> 
> This sounds like something which someone has actually triggered in a
> real-world situation.  So I added a cc:stable.  Please let me know if
> that was inappropriate.
> 
> And please remember to always include all information regarding
> end-user impact when fixing bugs.
> 
This bug fix is applicable to versions starting from v4.6