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From: Andrey Konovalov <andreyknvl@google.com>
To: Oliver Neukum <oneukum@suse.com>
Cc: syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	steve_bayless@keysight.com,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	guido.kiener@rohde-schwarz.com,
	syzbot <syzbot+55b0304b360654a7537b@syzkaller.appspotmail.com>,
	USB list <linux-usb@vger.kernel.org>
Subject: Re: divide error in usbtmc_generic_read
Date: Mon, 19 Aug 2019 14:43:05 +0200
Message-ID: <CAAeHK+xX3vk_JoJ=2tHF__LECxNmPXuPMkxWz6u+K6L-MdN=9g@mail.gmail.com> (raw)
In-Reply-To: <1566218263.5663.22.camel@suse.com>

On Mon, Aug 19, 2019 at 2:37 PM Oliver Neukum <oneukum@suse.com> wrote:
>
> Am Montag, den 19.08.2019, 14:17 +0200 schrieb Andrey Konovalov:
> > On Thu, Aug 15, 2019 at 3:31 PM Oliver Neukum <oneukum@suse.com> wrote:
> > >
> > > Am Mittwoch, den 14.08.2019, 06:38 -0700 schrieb syzbot:
> > > > syzbot has tested the proposed patch but the reproducer still triggered
> > > > crash:
> > > > KASAN: use-after-free Read in usbtmc_disconnect
> > >
> > > I am afraid that is a difficiency in KASAN that should be fixed.
> > > Is the class of the error compared if I leave in more of the
> > > original bug report? Actually the ID is still there, so it really
> > > should return an inconclusive in these cases.
> >
> > I don't get this, what kind of deficiency do you mean?
>
> The original error was a divide by zero. The first fix fixed that
> but still another error showed up. If I propose a fix there are
> other possibilities besides it working.
>
> I could have no effect on the original bug or my fix breaks
> something else and KASAN is making no difference between
> those cases.

I think you mean syzbot here and not KASAN. Do I understand correctly,
that you're saying that the original report was divide-by-zero, but
when you requested to test the patch the reproducer triggered a
use-after-free, and syzbot didn't treat the patch you provided as a
correct fix? In this case this is working as intended, as a bug
(especially some race) can manifest in different ways, so the kernel
might crash with a different stack trace.

  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-14 11:38 syzbot
2019-08-14 13:25 ` Oliver Neukum
2019-08-14 13:38   ` syzbot
2019-08-14 13:52     ` Andrey Konovalov
2019-08-15 13:31     ` Oliver Neukum
2019-08-19 12:17       ` Andrey Konovalov
2019-08-19 12:37         ` Oliver Neukum
2019-08-19 12:43           ` Andrey Konovalov [this message]
2019-08-19 13:09             ` Oliver Neukum
2019-08-19 13:18               ` Andrey Konovalov
2019-08-19 13:49                 ` Oliver Neukum
2019-08-19 15:40                   ` Andrey Konovalov
2019-08-20  9:01                     ` Oliver Neukum
2019-08-15 14:28 ` Oliver Neukum
2019-08-15 14:48   ` syzbot
2019-11-19 13:35 ` Andrey Konovalov

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