From: syzbot <syzbot+7b47f87674e9a1569110@syzkaller.appspotmail.com>
To: andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
daniel@iogearbox.net, eddyz87@gmail.com, emil@etsalapatis.com,
ihor.solodrai@linux.dev, jolsa@kernel.org,
linux-kernel@vger.kernel.org, martin.lau@linux.dev,
memxor@gmail.com, netdev@vger.kernel.org, song@kernel.org,
syzkaller-bugs@googlegroups.com, yonghong.song@linux.dev
Subject: [syzbot] [bpf?] WARNING in bpf_mark_chain_precision
Date: Fri, 04 Sep 2026 07:14:36 -0700 [thread overview]
Message-ID: <6a9ad24c.b5d4176b.238c3e.0001.GAE@google.com> (raw)
Hello,
syzbot found the following issue on:
HEAD commit: e044668419b9 Merge branch 'misc-bug-fixes-part-1'
git tree: bpf
console+strace: https://syzkaller.appspot.com/x/log.txt?x=162038f9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=13dd96f4206498c4
dashboard link: https://syzkaller.appspot.com/bug?extid=7b47f87674e9a1569110
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=165fcb49580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=112038f9580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2c0c9fa35baf/disk-e0446684.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1ed2d74549a1/vmlinux-e0446684.xz
kernel image: https://storage.googleapis.com/syzbot-assets/479e5164ed3b/bzImage-e0446684.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7b47f87674e9a1569110@syzkaller.appspotmail.com
------------[ cut here ]------------
verifier bug: backtracking misuse
WARNING: kernel/bpf/backtrack.c:829 at bpf_mark_chain_precision+0x571b/0x76b0 kernel/bpf/backtrack.c:829, CPU#1: syz-executor403/5624
Modules linked in:
CPU: 1 UID: 0 PID: 5624 Comm: syz-executor403 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:bpf_mark_chain_precision+0x571b/0x76b0 kernel/bpf/backtrack.c:829
Code: ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c 16 ff ff ff 48 89 df e8 76 17 44 00 e9 09 ff ff ff e8 0c d0 d4 ff 48 8d 3d b5 50 6a 0e <67> 48 0f b9 3a 48 8b 3c 24 48 81 c7 88 08 00 00 48 c7 c6 a0 c6 f6
RSP: 0018:ffffc90003957228 EFLAGS: 00010293
RAX: ffffffff81f23d54 RBX: 0000000000000001 RCX: ffff88807f7b9f40
RDX: 0000000000000000 RSI: 0000000000000003 RDI: ffffffff905c8e10
RBP: 0000000000000003 R08: ffff88807f7b9f40 R09: 0000000000000003
R10: 0000000000000007 R11: 0000000000000000 R12: ffff88807f4f3050
R13: dffffc0000000000 R14: 0000000000000001 R15: 0000000000000000
FS: 00005555805e0400(0000) GS:ffff888125024000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006a9ee0 CR3: 000000007133a000 CR4: 00000000003526f0
Call Trace:
<TASK>
mark_chain_precision kernel/bpf/verifier.c:3373 [inline]
check_helper_call kernel/bpf/verifier.c:10894 [inline]
do_check_insn+0x12a74/0x17c20 kernel/bpf/verifier.c:18177
do_check kernel/bpf/verifier.c:18363 [inline]
do_check_common+0x3c19/0x5d30 kernel/bpf/verifier.c:19444
do_check_main kernel/bpf/verifier.c:19540 [inline]
bpf_check+0x2639/0x2e10 kernel/bpf/verifier.c:21195
bpf_prog_load+0x14d6/0x1c20 kernel/bpf/syscall.c:3133
__sys_bpf+0xd0d/0xd90 kernel/bpf/syscall.c:6367
__do_sys_bpf kernel/bpf/syscall.c:6486 [inline]
__se_sys_bpf kernel/bpf/syscall.c:6483 [inline]
__x64_sys_bpf+0xba/0xd0 kernel/bpf/syscall.c:6483
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4f25cf1749
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 0f 1f 44 00 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff991a6f18 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f4f25cf1749
RDX: 0000000000000080 RSI: 0000200000000300 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000006 R09: 0000000000000006
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f4f25d84c40 R15: 0000000000000002
</TASK>
----------------
Code disassembly (best guess):
0: ff 89 d9 80 e1 07 decl 0x7e180d9(%rcx)
6: 80 c1 03 add $0x3,%cl
9: 38 c1 cmp %al,%cl
b: 0f 8c 16 ff ff ff jl 0xffffff27
11: 48 89 df mov %rbx,%rdi
14: e8 76 17 44 00 call 0x44178f
19: e9 09 ff ff ff jmp 0xffffff27
1e: e8 0c d0 d4 ff call 0xffd4d02f
23: 48 8d 3d b5 50 6a 0e lea 0xe6a50b5(%rip),%rdi # 0xe6a50df
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: 48 8b 3c 24 mov (%rsp),%rdi
33: 48 81 c7 88 08 00 00 add $0x888,%rdi
3a: 48 rex.W
3b: c7 .byte 0xc7
3c: c6 (bad)
3d: a0 .byte 0xa0
3e: c6 (bad)
3f: f6 .byte 0xf6
---
This report is generated by a bot. It may contain errors.
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reply other threads:[~2026-09-04 14:14 UTC|newest]
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