Message-ID: <aM1moP0fr7GrlbWZ@mail.gmail.com>
Date: Fri, 19 Sep 2025 16:20:16 +0200
From: Paul Chaignon <paul.chaignon@...il.com>
To: syzbot <syzbot+e1fa4a4a9361f2f3bbd6@...kaller.appspotmail.com>
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
	daniel@...earbox.net, eddyz87@...il.com, haoluo@...gle.com,
	john.fastabend@...il.com, jolsa@...nel.org, kpsingh@...nel.org,
	linux-kernel@...r.kernel.org, martin.lau@...ux.dev, sdf@...ichev.me,
	song@...nel.org, syzkaller-bugs@...glegroups.com,
	yonghong.song@...ux.dev
Subject: Re: [syzbot] [bpf?] WARNING in do_check (2)

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git a3c73d629ea1373af3c0c954d41fd1af555492e3

On Mon, Sep 15, 2025 at 11:29:33AM -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=11d1947c580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4d8792ecb6308d0f
> dashboard link: https://syzkaller.appspot.com/bug?extid=e1fa4a4a9361f2f3bbd6
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1355f934580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12170e42580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/f8eff1302251/disk-f83ec76b.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/1009d8f3246e/vmlinux-f83ec76b.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/5ba227871658/bzImage-f83ec76b.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+e1fa4a4a9361f2f3bbd6@...kaller.appspotmail.com
> 
> ------------[ cut here ]------------
> verifier bug: scc exit: no visit info for call chain (1)(1)
> WARNING: CPU: 0 PID: 6062 at kernel/bpf/verifier.c:1950 maybe_exit_scc kernel/bpf/verifier.c:1949 [inline]
> WARNING: CPU: 0 PID: 6062 at kernel/bpf/verifier.c:1950 update_branch_counts kernel/bpf/verifier.c:2040 [inline]
> WARNING: CPU: 0 PID: 6062 at kernel/bpf/verifier.c:1950 do_check+0xe228/0xe520 kernel/bpf/verifier.c:20135
> Modules linked in:
> CPU: 0 UID: 0 PID: 6062 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 kernel/bpf/verifier.c:1949 [inline]
> RIP: 0010:update_branch_counts kernel/bpf/verifier.c:2040 [inline]
> RIP: 0010:do_check+0xe228/0xe520 kernel/bpf/verifier.c:20135
> Code: c6 05 35 d3 b6 0d 01 90 48 8b 7c 24 10 48 8b b4 24 e0 00 00 00 e8 28 8e 00 00 48 c7 c7 80 f6 91 8b 48 89 c6 e8 a9 a1 ac ff 90 <0f> 0b 90 90 e9 a8 fc ff ff e8 9a 04 e9 ff c6 05 c1 d2 b6 0d 01 90
> RSP: 0018:ffffc90003b9f1c0 EFLAGS: 00010246
> RAX: bb0e1817e9dd7600 RBX: 0000000000000000 RCX: ffff88802faf0000
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
> RBP: ffffc90003b9f528 R08: 0000000000000003 R09: 0000000000000004
> R10: dffffc0000000000 R11: fffffbfff1bfa22c R12: dffffc0000000000
> R13: ffffc90000a7e0a0 R14: 0000000000000000 R15: ffff88805b1ebd00
> FS:  00005555720d8500(0000) GS:ffff888125c15000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000200000003000 CR3: 0000000075b7d000 CR4: 0000000000350ef0
> Call Trace:
>  <TASK>
>  do_check_common+0x1949/0x24f0 kernel/bpf/verifier.c:23264
>  do_check_main kernel/bpf/verifier.c:23347 [inline]
>  bpf_check+0x1746a/0x1d2d0 kernel/bpf/verifier.c:24707
>  bpf_prog_load+0x1318/0x1930 kernel/bpf/syscall.c:2979
>  __sys_bpf+0x528/0x870 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+0x7c/0x90 kernel/bpf/syscall.c:6137
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7ff4c0d8eba9
> 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:00007ffeb05e37d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 00007ff4c0fd5fa0 RCX: 00007ff4c0d8eba9
> RDX: 0000000000000048 RSI: 00002000000017c0 RDI: 0000000000000005
> RBP: 00007ff4c0e11e19 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ff4c0fd5fa0 R14: 00007ff4c0fd5fa0 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@...glegroups.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
> 

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