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([2620:10d:c090:500::4:283f]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-265819a6193sm50361505ad.55.2025.09.15.15.34.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Sep 2025 15:34:30 -0700 (PDT) Message-ID: <81bb1cf72e9c5f56c92ab43636a0626a1046d748.camel@gmail.com> Subject: Re: [syzbot] [bpf?] WARNING in maybe_exit_scc From: Eduard Zingerman To: syzbot , 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 Date: Mon, 15 Sep 2025 15:34:28 -0700 In-Reply-To: <68c85acd.050a0220.2ff435.03a4.GAE@google.com> References: <68c85acd.050a0220.2ff435.03a4.GAE@google.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-1.fc42) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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=3D137d0e4258000= 0 > kernel config: https://syzkaller.appspot.com/x/.config?x=3D8f01d8629880e= 620 > dashboard link: https://syzkaller.appspot.com/bug?extid=3D3afc814e8df1af6= 4b653 > compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binuti= ls for Debian) 2.40 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=3D104a947c580= 000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=3D14467b6258000= 0 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/be9b26c66bc1/dis= k-f83ec76b.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/53dc5627e608/vmlinu= x-f83ec76b.xz > kernel image: https://storage.googleapis.com/syzbot-assets/398506a67fd8/b= zImage-f83ec76b.xz > > IMPORTANT: if you fix the issue, please add the following tag to the comm= it: > 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+0x= 768/0x8d0 kernel/bpf/verifier.c:1949 Both this and [1] are reported for very similar programs: <[1]> ---------------------------------------------------------------------------= ----------------- (b7) r0 =3D -1023213567 (b7) r0 =3D -1023213567 = =09 (bf) r3 =3D r10 (bf) r3 =3D r10 =09 (07) r3 +=3D -512 (07) r3 +=3D -504 =09 (72) *(u8 *)(r10 -16) =3D -8 (72) *(u8 *)(r10 -16) =3D -8 =09 (71) r4 =3D *(u8 *)(r10 -16) (71) r4 =3D *(u8 *)(r10 -16) =09 (65) if r4 s> 0xff000000 goto pc+2 (65) if r4 s> 0xff000000 goto pc+2 = =09 (2d) if r0 > r4 goto pc+5 (2d) if r0 > r4 goto pc+5 =09 (20) r0 =3D *(u32 *)skb[60673] (20) r0 =3D *(u32 *)skb[60673] =09 (7b) *(u64 *)(r3 +0) =3D r0 (7b) *(u64 *)(r3 +0) =3D r0 =09 (1d) if r4 =3D=3D r4 goto pc+0 (1d) if r4 =3D=3D r4 goto pc+0 =09 (7a) *(u64 *)(r10 -512) =3D -256 (7a) *(u64 *)(r10 -512) =3D -256 = =09 (db) lock *(u64 *)(r3 +0) |=3D r0 (db) r0 =3D atomic64_fetch_and((u64 = *)(r3 +0), r0)=09 (b5) if r0 <=3D 0x0 goto pc-2 (b5) if r0 <=3D 0x0 goto pc-2 =09 (95) exit (95) exit =09 So, I assume it's the same issue. Looking into it. [1] https://lore.kernel.org/bpf/68c85b0d.050a0220.2ff435.03a5.GAE@google.co= m/T/#u > Modules linked in: > CPU: 1 UID: 0 PID: 6013 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(f= ull) > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS G= oogle 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 f= 8 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:0000000000000= 000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 000055557c9b5808 CR3: 0000000073b4d000 CR4: 00000000003526f0 > Call Trace: > > 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 f= 7 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 > > > > --- > 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