Subject: Re: [syzbot] KASAN: slab-out-of-bounds Read in copy_data

From: "Michael S. Tsirkin" <[email-masked]>
Date: Wed, 27 Oct 2021 11:28:48 -0400

On Wed, Oct 27, 2021 at 03:36:19PM +0200, Dmitry Vyukov wrote:
> On Wed, 27 Oct 2021 at 15:11, Laurent Vivier <[email-masked]> wrote:
> >
> > On 26/10/2021 18:39, syzbot wrote:
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit:    9ae1fbdeabd3 Add linux-next specific files for 20211025
> > > git tree:       linux-next
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=1331363cb00000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=aeb17e42bc109064
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=b86736b5935e0d25b446
> > > compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=116ce954b00000
> > > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=132fcf62b00000
> > >
> > > The issue was bisected to:
> > >
> > > commit 22849b5ea5952d853547cc5e0651f34a246b2a4f
> > > Author: Leon Romanovsky <[email-masked]>
> > > Date:   Thu Oct 21 14:16:14 2021 +0000
> > >
> > >      devlink: Remove not-executed trap policer notifications
> > >
> > > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=137d8bfcb00000
> > > final oops:     https://syzkaller.appspot.com/x/report.txt?x=10fd8bfcb00000
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=177d8bfcb00000
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: [email-masked]
> > > Fixes: 22849b5ea595 ("devlink: Remove not-executed trap policer notifications")
> > >
> > > ==================================================================
> > > BUG: KASAN: slab-out-of-bounds in memcpy include/linux/fortify-string.h:225 [inline]
> > > BUG: KASAN: slab-out-of-bounds in copy_data+0xf3/0x2e0 drivers/char/hw_random/virtio-rng.c:68
> > > Read of size 64 at addr ffff88801a7a1580 by task syz-executor989/6542
> > >
> >
> > I'm not able to reproduce the problem with next-20211026 and the C reproducer.
> >
> > And reviewing the code in copy_data() I don't see any issue.
> >
> > Is it possible to know what it the VM configuration used to test it?
> 
> Hi Laurent,
> 
> syzbot used e2-standard-2 GCE VM when that happened.
> You can see some info about these VMs under the "VM info" link on the dashboard.

Could you pls confirm whether reverting
caaf2874ba27b92bca6f0298bf88bad94067ec37 addresses this?