linux-kernel - Re: [PATCH V2] drivers/media/v4l2-core/videobuf2-core.c: fix error return code

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Date:	Thu, 18 Oct 2012 17:39:39 +0200
From:	Peter Senna Tschudin <peter.senna@...il.com>
To:	Ezequiel Garcia <elezegarcia@...il.com>
Cc:	pawel@...iak.com, m.szyprowski@...sung.com,
	kyungmin.park@...sung.com, mchehab@...radead.org,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH V2] drivers/media/v4l2-core/videobuf2-core.c: fix error
 return code

On Thu, Oct 18, 2012 at 5:28 PM, Ezequiel Garcia <elezegarcia@...il.com> wrote:
> On Thu, Oct 18, 2012 at 11:47 AM, Peter Senna Tschudin
> <peter.senna@...il.com> wrote:
>> This patch fixes a NULL pointer dereference bug at __vb2_init_fileio().
>> The NULL pointer deference happens at videobuf2-core.c:
>>
>> static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_t count,
>>                 loff_t *ppos, int nonblock, int read)
>> {
>> ...
>>         if (!q->fileio) {
>>                 ret = __vb2_init_fileio(q, read);
>>                 dprintk(3, "file io: vb2_init_fileio result: %d\n", ret);
>>                 if (ret)
>>                         return ret;
>>         }
>>         fileio = q->fileio; // NULL pointer deference here
>> ...
>> }
>>
>> It was tested with vivi driver and qv4l2 for selecting read() as capture method.
>> The OOPS happened when I've artificially forced the error by commenting the line:
>>         if (fileio->bufs[i].vaddr == NULL)
>>
>
> ... but if you manually changed the original source, how
> can this be a real BUG?

It is supposed that under some circumstances, (fileio->bufs[i].vaddr
== NULL) can be true. 'While testing', my change forced the scenario
in which (fileio->bufs[i].vaddr == NULL) is true...

>
> Or am I missing something here ?
>
>     Ezequiel



-- 
Peter
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