On Tue, Nov 13, 2018 at 12:56:18PM +0100, Hans Verkuil wrote:
> 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@xxxxxxxxx>
> >> Reported-by: syzbot+4180ff9ca6810b06c1e9@xxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > Acked-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
>
> Sorry:
>
> Nacked-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
>
> 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
>
Hi Hans,
Thanks for explaining the root cause. I was also thinking a similar
patch with your second one. It looks like the reported syzbot is needed
to be added to your first patch.
Regards,
Myungho
> >
> > 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
> >
>
