Messages in this thread | | | Date | Tue, 10 Dec 2019 15:13:28 -0500 (EST) | From | Alan Stern <> | Subject | Re: KASAN: use-after-free Read in usbvision_v4l2_open |
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On Tue, 10 Dec 2019, Andrey Konovalov wrote:
> On Tue, Dec 10, 2019 at 8:48 PM Alan Stern <stern@rowland.harvard.edu> 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@google.com> and the other with message ID <000000000000441a4205995eca11@google.com>? It seems like overkill.
Alan Stern
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