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

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Date:   Wed, 27 Oct 2021 15:11:02 +0200
From:   Laurent Vivier <lvivier@...hat.com>
To:     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 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?

Thanks,
Laurent