From: Johan Hovold <johan@kernel.org>
To: syzbot <syzbot+0243cb250a51eeefb8cc@syzkaller.appspotmail.com>
Cc: andreyknvl@google.com, dmg@turingmachine.org,
gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
linux-usb@vger.kernel.org, syzkaller-bugs@googlegroups.com
Subject: Re: KASAN: use-after-free Read in adu_disconnect
Date: Fri, 20 Sep 2019 10:26:31 +0200 [thread overview]
Message-ID: <20190920082631.GL30545@localhost> (raw)
In-Reply-To: <20190919103504.GC30545@localhost>
On Thu, Sep 19, 2019 at 12:35:04PM +0200, Johan Hovold wrote:
> On Fri, Aug 09, 2019 at 01:24:04PM -0700, syzbot wrote:
> > syzbot has found a reproducer for the following crash on:
> >
> > HEAD commit: e96407b4 usb-fuzzer: main usb gadget fuzzer driver
> > git tree: https://github.com/google/kasan.git usb-fuzzer
> > console output: https://syzkaller.appspot.com/x/log.txt?x=13871a4a600000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
> > dashboard link: https://syzkaller.appspot.com/bug?extid=0243cb250a51eeefb8cc
> > compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11c4c8e2600000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11d80d2c600000
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+0243cb250a51eeefb8cc@syzkaller.appspotmail.com
> >
> > usb 1-1: USB disconnect, device number 4
> > ==================================================================
> > BUG: KASAN: use-after-free in atomic64_read
> > include/asm-generic/atomic-instrumented.h:836 [inline]
> > BUG: KASAN: use-after-free in atomic_long_read
> > include/asm-generic/atomic-long.h:28 [inline]
> > BUG: KASAN: use-after-free in __mutex_unlock_slowpath+0x96/0x670
> > kernel/locking/mutex.c:1211
> > Read of size 8 at addr ffff8881d1d0aa00 by task kworker/0:1/12
>
> Should be fixed by the below patch.
>
> #syz test: https://github.com/google/kasan.git f0df5c1b
Hmm. Let's try that again with the commit id from the report...
#syz test: https://github.com/google/kasan.git e96407b4
Johan
> From 6f09430ae18085a1552fc641e53d3a3e678db6f3 Mon Sep 17 00:00:00 2001
> From: Johan Hovold <johan@kernel.org>
> Date: Thu, 19 Sep 2019 11:48:38 +0200
> Subject: [PATCH] USB: adutux: fix use-after-free on disconnect
>
> The driver was clearing its struct usb_device pointer, which it uses as
> an inverted disconnected flag, before deregistering the character device
> and without serialising against racing release().
>
> This could lead to a use-after-free if a racing release() callback
> observes the cleared pointer and frees the driver data before
> disconnect() is finished with it.
>
> This could also lead to NULL-pointer dereferences in a racing open().
>
> Fixes: f08812d5eb8f ("USB: FIx locks and urb->status in adutux (updated)")
> Reported-by: syzbot+0243cb250a51eeefb8cc@syzkaller.appspotmail.com
> Cc: stable <stable@vger.kernel.org> # 2.6.24
> Signed-off-by: Johan Hovold <johan@kernel.org>
> ---
>
> drivers/usb/misc/adutux.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/misc/adutux.c b/drivers/usb/misc/adutux.c
> index 344d523b0502..bcc138990e2f 100644
> --- a/drivers/usb/misc/adutux.c
> +++ b/drivers/usb/misc/adutux.c
> @@ -762,14 +762,15 @@ static void adu_disconnect(struct usb_interface *interface)
>
> dev = usb_get_intfdata(interface);
>
> - mutex_lock(&dev->mtx); /* not interruptible */
> - dev->udev = NULL; /* poison */
> usb_deregister_dev(interface, &adu_class);
> - mutex_unlock(&dev->mtx);
>
> mutex_lock(&adutux_mutex);
> usb_set_intfdata(interface, NULL);
>
> + mutex_lock(&dev->mtx); /* not interruptible */
> + dev->udev = NULL; /* poison */
> + mutex_unlock(&dev->mtx);
> +
> /* if the device is not opened, then we clean up right now */
> if (!dev->open_count)
> adu_delete(dev);
next prev parent reply other threads:[~2019-09-20 8:26 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-05 11:58 KASAN: use-after-free Read in adu_disconnect syzbot
2019-08-09 20:24 ` syzbot
2019-09-19 10:35 ` Johan Hovold
2019-09-19 10:53 ` syzbot
2019-09-20 8:26 ` Johan Hovold [this message]
2019-09-20 9:02 ` syzbot
2019-09-20 9:08 ` Johan Hovold
2019-09-20 9:13 ` Dmitry Vyukov
2019-09-20 9:21 ` Johan Hovold
2019-09-20 9:28 ` Dmitry Vyukov
2019-09-20 9:35 ` Johan Hovold
2019-09-20 10:05 ` Dmitry Vyukov
2019-09-20 9:20 ` syzbot
2019-09-20 10:02 ` Johan Hovold
2019-09-20 10:08 ` Dmitry Vyukov
2019-09-20 10:16 ` Andrey Konovalov
2019-09-20 14:31 ` Johan Hovold
2019-09-20 10:21 ` syzbot
2019-09-20 14:38 ` Johan Hovold
2019-09-20 14:58 ` syzbot
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