linux-kernel - Re: KASAN: use-after-free Read in cpia2_usb

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Message-ID: <20190703171008.GA10080@gmail.com>
Date:   Wed, 3 Jul 2019 10:10:09 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Oliver Neukum <oneukum@...e.com>
Cc:     syzbot <syzbot+0c90fc937c84f97d0aa6@...kaller.appspotmail.com>,
        keescook@...omium.org, andreyknvl@...gle.com,
        syzkaller-bugs@...glegroups.com, mchehab@...nel.org,
        tglx@...utronix.de, sakari.ailus@...ux.intel.com,
        kstewart@...uxfoundation.org, allison@...utok.net,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-usb@...r.kernel.org, hverkuil-cisco@...all.nl
Subject: Re: KASAN: use-after-free Read in cpia2_usb_disconnect

On Wed, Jul 03, 2019 at 09:42:09AM +0200, Oliver Neukum wrote:
> Am Dienstag, den 02.07.2019, 18:01 -0700 schrieb syzbot:
> > syzbot has found a reproducer for the following crash on:
> > 
> > HEAD commit:    7829a896 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=11e19043a00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=f6d4561982f71f63
> > dashboard link: https://syzkaller.appspot.com/bug?extid=0c90fc937c84f97d0aa6
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=147d42eda00000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=104c268ba00000
> > 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+0c90fc937c84f97d0aa6@...kaller.appspotmail.com
> > 
> > cpia2: Message: count = 1, register[0] = 0x0
> > cpia2: Unexpected error: -19
> > ==================================================================
> > BUG: KASAN: use-after-free in cpia2_usb_disconnect+0x1a4/0x1c0  
> > drivers/media/usb/cpia2/cpia2_usb.c:898
> > Read of size 8 at addr ffff8881cf6c4e50 by task kworker/1:1/22
> 
> Please try this:
> 
> From a0a73298fc23acb95e7b6487e960be707563eb34 Mon Sep 17 00:00:00 2001
> From: Oliver Neukum <oneukum@...e.com>
> Date: Wed, 8 May 2019 12:36:40 +0200
> Subject: [PATCH] cpia2_usb: first wake up, then free in disconnect
> 

Who are you talking to?  If you want syzbot to test your patch, follow the
directions at https://github.com/google/syzkaller/blob/master/docs/syzbot.md#testing-patches

- Eric