From: Eduard Zingerman <eddyz87@gmail.com>
To: syzbot <syzbot+3afc814e8df1af64b653@syzkaller.appspotmail.com>,
andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
daniel@iogearbox.net, haoluo@google.com,
john.fastabend@gmail.com, jolsa@kernel.org, kpsingh@kernel.org,
linux-kernel@vger.kernel.org, martin.lau@linux.dev,
sdf@fomichev.me, song@kernel.org,
syzkaller-bugs@googlegroups.com, yonghong.song@linux.dev
Subject: Re: [syzbot] [bpf?] WARNING in maybe_exit_scc
Date: Mon, 15 Sep 2025 15:34:28 -0700 [thread overview]
Message-ID: <81bb1cf72e9c5f56c92ab43636a0626a1046d748.camel@gmail.com> (raw)
In-Reply-To: <68c85acd.050a0220.2ff435.03a4.GAE@google.com>
On Mon, 2025-09-15 at 11:28 -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: f83ec76bf285 Linux 6.17-rc6
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=137d0e42580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=8f01d8629880e620
> dashboard link: https://syzkaller.appspot.com/bug?extid=3afc814e8df1af64b653
> compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=104a947c580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14467b62580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/be9b26c66bc1/disk-f83ec76b.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/53dc5627e608/vmlinux-f83ec76b.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/398506a67fd8/bzImage-f83ec76b.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+3afc814e8df1af64b653@syzkaller.appspotmail.com
>
> ------------[ cut here ]------------
> verifier bug: scc exit: no visit info for call chain (1)(1)
> WARNING: CPU: 1 PID: 6013 at kernel/bpf/verifier.c:1949 maybe_exit_scc+0x768/0x8d0 kernel/bpf/verifier.c:1949
Both this and [1] are reported for very similar programs:
<this> <[1]>
--------------------------------------------------------------------------------------------
(b7) r0 = -1023213567 (b7) r0 = -1023213567
(bf) r3 = r10 (bf) r3 = r10
(07) r3 += -512 (07) r3 += -504
(72) *(u8 *)(r10 -16) = -8 (72) *(u8 *)(r10 -16) = -8
(71) r4 = *(u8 *)(r10 -16) (71) r4 = *(u8 *)(r10 -16)
(65) if r4 s> 0xff000000 goto pc+2 (65) if r4 s> 0xff000000 goto pc+2
(2d) if r0 > r4 goto pc+5 (2d) if r0 > r4 goto pc+5
(20) r0 = *(u32 *)skb[60673] (20) r0 = *(u32 *)skb[60673]
(7b) *(u64 *)(r3 +0) = r0 (7b) *(u64 *)(r3 +0) = r0
(1d) if r4 == r4 goto pc+0 (1d) if r4 == r4 goto pc+0
(7a) *(u64 *)(r10 -512) = -256 (7a) *(u64 *)(r10 -512) = -256
(db) lock *(u64 *)(r3 +0) |= r0 (db) r0 = atomic64_fetch_and((u64 *)(r3 +0), r0)
(b5) if r0 <= 0x0 goto pc-2 (b5) if r0 <= 0x0 goto pc-2
(95) exit (95) exit
So, I assume it's the same issue. Looking into it.
[1] https://lore.kernel.org/bpf/68c85b0d.050a0220.2ff435.03a5.GAE@google.com/T/#u
> Modules linked in:
> CPU: 1 UID: 0 PID: 6013 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
> RIP: 0010:maybe_exit_scc+0x768/0x8d0 kernel/bpf/verifier.c:1949
> Code: ff ff e8 cb 8e e7 ff c6 05 0a b5 bf 0e 01 90 48 89 ee 48 89 df e8 f8 41 fb ff 48 c7 c7 a0 9b b5 8b 48 89 c6 e8 59 33 a6 ff 90 <0f> 0b 90 90 e9 4e ff ff ff e8 0a ee 4d 00 e9 7f f9 ff ff 4c 8b 4c
> RSP: 0018:ffffc900041bf500 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: ffff888079840000 RCX: ffffffff817a4388
> RDX: ffff88807d3f8000 RSI: ffffffff817a4395 RDI: 0000000000000001
> RBP: ffff888079846328 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000001 R11: 0000000000000000 R12: 1ffff92000837ea7
> R13: 0000000000000000 R14: ffff88805cf87400 R15: dffffc0000000000
> FS: 000055557c9b5500(0000) GS:ffff8881247b2000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000055557c9b5808 CR3: 0000000073b4d000 CR4: 00000000003526f0
> Call Trace:
> <TASK>
> update_branch_counts kernel/bpf/verifier.c:2040 [inline]
> do_check kernel/bpf/verifier.c:20135 [inline]
> do_check_common+0x20cc/0xb410 kernel/bpf/verifier.c:23264
> do_check_main kernel/bpf/verifier.c:23347 [inline]
> bpf_check+0x869f/0xc670 kernel/bpf/verifier.c:24707
> bpf_prog_load+0xe41/0x2490 kernel/bpf/syscall.c:2979
> __sys_bpf+0x4a3f/0x4de0 kernel/bpf/syscall.c:6029
> __do_sys_bpf kernel/bpf/syscall.c:6139 [inline]
> __se_sys_bpf kernel/bpf/syscall.c:6137 [inline]
> __x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:6137
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fd1d078eba9
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffee0400aa8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 00007fd1d09d5fa0 RCX: 00007fd1d078eba9
> RDX: 0000000000000048 RSI: 00002000000017c0 RDI: 0000000000000005
> RBP: 00007fd1d0811e19 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fd1d09d5fa0 R14: 00007fd1d09d5fa0 R15: 0000000000000003
> </TASK>
>
>
> ---
> 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@googlegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup
next prev parent reply other threads:[~2025-09-15 22:34 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-15 18:28 syzbot
2025-09-15 22:34 ` Eduard Zingerman [this message]
2025-09-15 23:40 ` Eduard Zingerman
2025-09-16 9:14 ` Eduard Zingerman
2025-09-16 10:20 ` syzbot
2025-09-29 7:57 ` Luis Gerhorst
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