Re: KASAN: use-after-free Read in adu_disconnect

[Johan Hovold]

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

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