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 16:38:55 +0200 [thread overview]
Message-ID: <20190920143855.GS30545@localhost> (raw)
In-Reply-To: <000000000000a12822058fb4f408@google.com>
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
Let's resend and retest using the latest usb-fuzzer kernel, which
includes the fix for a couple char dev races that we were now hitting:
#syz test: https://github.com/google/kasan.git e0bd8d79
I'll fix the failure to stop I/O at disconnect separately.
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);
--
2.23.0
next prev parent reply other threads:[~2019-09-20 14:39 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
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 [this message]
2019-09-20 14:58 ` syzbot
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