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@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > 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@xxxxxxxxxx> > 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@xxxxxxxxxxxxxxxxxxxxxxxxx > Cc: stable <stable@xxxxxxxxxxxxxxx> # 2.6.24 > Signed-off-by: Johan Hovold <johan@xxxxxxxxxx> > --- > > 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);
