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SubjectRe: [PATCH] media: videobuf2-core: Fix error handling when fileio is deallocated
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On 11/13/18 11:27, Marek Szyprowski wrote:
> Hi Myungho,
>
> On 2018-11-12 01:49, Myungho Jung wrote:
>> The mutex that is held from vb2_fop_read() can be unlocked while waiting
>> for a buffer if the queue is streaming and blocking. Meanwhile, fileio
>> can be released. So, it should return an error if the fileio address is
>> changed.
>>
>> Signed-off-by: Myungho Jung <mhjungk@gmail.com>
>> Reported-by: syzbot+4180ff9ca6810b06c1e9@syzkaller.appspotmail.com
>
> Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>

Sorry:

Nacked-by: Hans Verkuil <hans.verkuil@cisco.com>

This addresses the symptom, not the underlying cause.

I have a patch that fixes the actual cause that I plan to post soon
after I review it a bit more.

Regards,

Hans

>
> Thanks for analyzing the code and fixing this issue!
>
>> ---
>> drivers/media/common/videobuf2/videobuf2-core.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
>> index 975ff5669f72..bff94752eb27 100644
>> --- a/drivers/media/common/videobuf2/videobuf2-core.c
>> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
>> @@ -2564,6 +2564,10 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
>> dprintk(5, "vb2_dqbuf result: %d\n", ret);
>> if (ret)
>> return ret;
>> + if (fileio != q->fileio) {
>> + dprintk(3, "fileio deallocated\n");
>> + return -EFAULT;
>> + }
>> fileio->dq_count += 1;
>>
>> fileio->cur_index = index;
>
> Best regards
>

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