linux-kernel - Re: Re: KASAN: use-after-free Read in usbvision_v4l2

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Date:   Wed, 11 Dec 2019 16:35:07 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     Andrey Konovalov <andreyknvl@...gle.com>,
        syzbot <syzbot+7fa38a608b1075dfd634@...kaller.appspotmail.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Souptick Joarder <jrdr.linux@...il.com>,
        Kernel development list <linux-kernel@...r.kernel.org>,
        linux-media@...r.kernel.org, USB list <linux-usb@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Richard Fontana <rfontana@...hat.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Re: KASAN: use-after-free Read in usbvision_v4l2_open

On Wed, Dec 11, 2019 at 4:15 PM Alan Stern <stern@...land.harvard.edu> wrote
>
> On Wed, 11 Dec 2019, Andrey Konovalov wrote:
>
> > On Tue, Dec 10, 2019 at 9:17 PM Alan Stern <stern@...land.harvard.edu> wrote:
> > >
> > > On Tue, 10 Dec 2019, syzbot wrote:
> > >
> > > > > On Mon, 9 Dec 2019, syzbot wrote:
> > > >
> > > > >> Hello,
> > > >
> > > > >> syzbot found the following crash on:
> > > >
> > > > >> HEAD commit:    1f22d15c usb: gadget: add raw-gadget interface
> > > > >> git tree:       https://github.com/google/kasan.git usb-fuzzer
> > > > >> console output: https://syzkaller.appspot.com/x/log.txt?x=1296f42ae00000
> > > > >> kernel config:
> > > > >> https://syzkaller.appspot.com/x/.config?x=8ccee2968018adcb
> > > > >> dashboard link:
> > > > >> https://syzkaller.appspot.com/bug?extid=c7b0ec009a216143df30
> > > > >> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > > >
> > > > >> Unfortunately, I don't have any reproducer for this crash yet.
> > > >
> > > > >> IMPORTANT: if you fix the bug, please add the following tag to the
> > > > >> commit:
> > > > >> Reported-by: syzbot+c7b0ec009a216143df30@...kaller.appspotmail.com
>
> > > > This crash does not have a reproducer. I cannot test it.
> > >
> > > Let's try the same patch with a different bug report -- one that has a
> > > reproducer.  I assume that syzbot gets the bug identity from the
> > > email's From: line (which has been updated acoordingly) rather than the
> > > Subject: line.
> >
> > Did you get a response for this test? I see the test attempt on the
> > dashboard (the patch failed to build), but I didn't get an email with
> > the result.
>
> No response so far.  On the other hand, syzbot has been a bit slow to
> respond to my tests recently (typical turnaround time is several
> hours).  I don't know what's going on.

The system is busy with bisections. Patch testing takes precedence
over bisection, but only after the current one finished. Bisections
can take a long time, up to days. The way it all works is a total hack
that one can put together in a few days.