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

[Sylwester Nawrocki <s.nawrocki@samsung.com>]

On 10/18/2012 05:28 PM, Ezequiel Garcia wrote:
> On Thu, Oct 18, 2012 at 11:47 AM, Peter Senna Tschudin
> <peter.senna@gmail.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?
> 
> Or am I missing something here ?

He just commented out this line to trigger the bug, i.e. to simulate
a situation where fileio->bufs[i].vaddr is NULL. Which is now not
handled properly.

--
Thanks,
Sylwester