On Wed, Dec 11, 2019 at 3:23 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > On Tue, Dec 10, 2019 at 9:13 PM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > > > On Tue, 10 Dec 2019, Andrey Konovalov wrote: > > > > > On Tue, Dec 10, 2019 at 8:48 PM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > This looks like a race in v4l2_open(): The function drops the > > > > videodev_lock mutex before calling the video driver's open routine, and > > > > the device can be unregistered during the short time between. > > > > > > > > This patch tries to make the race much more likely to happen, for > > > > testing and verification. > > > > > > > > Andrey, will syzbot run the same test with this patch, even though it > > > > says it doesn't have a reproducer? > > > > > > Hi Alan, > > > > > > No, unfortunately there's nothing to run if there's no reproducer. > > > It's technically possible to run the same program log that triggered > > > the bug initially, but since the bug wasn't reproduced with this log > > > even without the patch, there isn't much sense in running it with the > > > patch applied. > > > > Actually it does make sense. That bug was caused by a race, and the > > patch tries to make the race much more likely to happen, so the same > > test should fail again. > > > > But never mind; I'll try a different approach. There's another syzbot > > bug report, one with a reproducer, and with this patch in place it > > should trigger the same race. I'll try submitting it that way. > > > > By the way, do you know why syzbot sent _two_ reply messages? One with > > message ID <00000000000031a0af05995eca0b@xxxxxxxxxx> and the other with > > message ID <000000000000441a4205995eca11@xxxxxxxxxx>? It seems like > > overkill. > > Hm, I'm not sure. Dmitry? I would assume it received 2 emails (second from syzkaller-bugs@ mailing list) and deduplication logic did not work somehow. So it replied to both.
