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

On 27/10/2021 09:20, Michael S. Tsirkin wrote:

On Wed, Oct 27, 2021 at 09:08:04AM +0200, Laurent Vivier wrote:

quoted

On 27/10/2021 00:34, Eric Dumazet wrote:

quoted

On 10/26/21 9:39 AM, syzbot wrote:

quoted

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 [off-list ref]
Date:   Thu Oct 21 14:16:14 2021 +0000

      devlink: Remove not-executed trap policer notifications

More likely this came with

caaf2874ba27b92bca6f0298bf88bad94067ec37 hwrng: virtio - don't waste entropy

I'm going to have a look.

Thanks,
Laurent

How bad is it if we just drop this and waste some bytes of entropy?

I don't think it's bad at all. In most of the cases we should use the full buffer.

So, you can drop, I will re-submit them later with a fix.

Thanks,
Laurent