linux-kernel - Re: [syzbot] KASAN: slab-out-of-bounds Read in copy

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Message-ID: <CACT4Y+amyT9dk-6iVqru-wQnotmwW=bt4VwaysgzjH9=PkxGww@mail.gmail.com>
Date:   Wed, 27 Oct 2021 15:36:19 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Laurent Vivier <lvivier@...hat.com>
Cc:     syzbot <syzbot+b86736b5935e0d25b446@...kaller.appspotmail.com>,
        davem@...emloft.net, herbert@...dor.apana.org.au, jiri@...dia.com,
        kuba@...nel.org, leonro@...dia.com, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, mpm@...enic.com, mst@...hat.com,
        netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] KASAN: slab-out-of-bounds Read in copy_data

On Wed, 27 Oct 2021 at 15:11, Laurent Vivier <lvivier@...hat.com> 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 <leonro@...dia.com>
> > 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: syzbot+b86736b5935e0d25b446@...kaller.appspotmail.com
> > 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.