linux-kernel - Re: [syzbot] [kernel?] net test error: UBSAN: negation-overflow in corrupted

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Message-ID: <CANp29Y4Zve8dohEhZ=12-w2SPOmOKbtt6U4MTvaK37CRrTQtMw@mail.gmail.com>
Date: Thu, 24 Apr 2025 14:55:54 +0200
From: Aleksandr Nogikh <nogikh@...gle.com>
To: syzbot <syzbot+76fd07ed2518fb9303f9@...kaller.appspotmail.com>, 
	Kees Cook <keescook@...gle.com>
Cc: akpm@...ux-foundation.org, davem@...emloft.net, kuba@...nel.org, 
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com, Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [syzbot] [kernel?] net test error: UBSAN: negation-overflow in corrupted

+ Kees Cook

Hi Kees,

This boot time error appears on v6.15-rc* when the kernel is built
with clang-20. It's apparently related to

commit ed2b548f1017586c44f50654ef9febb42d491f31
Author: Kees Cook <kees@...nel.org>
Date:   Thu Mar 6 20:19:09 2025 -0800
    ubsan/overflow: Rework integer overflow sanitizer option to turn
on everything

Could you please have a look whether it's a legit issue?

On Thu, Apr 24, 2025 at 2:51 PM syzbot
<syzbot+76fd07ed2518fb9303f9@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    cc0dec3f659d Merge branch 'net-stmmac-fix-timestamp-snapsh..
> git tree:       net
> console output: https://syzkaller.appspot.com/x/log.txt?x=131c21b3980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ac0f76cd0f8e093a
> dashboard link: https://syzkaller.appspot.com/bug?extid=76fd07ed2518fb9303f9
> compiler:       Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/1d6f321414b4/disk-cc0dec3f.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/072c28c931b0/vmlinux-cc0dec3f.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/bcb44ff40c55/bzImage-cc0dec3f.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+76fd07ed2518fb9303f9@...kaller.appspotmail.com
>
> virtio-scsi blksize=512 sectors=4194304 = 2048 MiB
> drive 0x000f27f0: PCHS=0/0/0 translation=lba LCHS=520/128/63 s=4194304
> Sending Seabios boot VM event.
> Booting from Hard Disk 0...
> [    0serialport: Connected to syzkaller.us-central1-c.ci-upstream-net-this-kasan-gce-test-1 port 1 (session ID: e72bd3249fa5f4b40b974e21e6d99e16e8384254f2e85c0fe39918dcc479fa4d, active connections: 1).
> .000000][    T0] UBSAN: negation-overflow in lib/sort.c:199:36
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this issue. See:
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>
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>
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>
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>
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