[syzbot] [bpf?] [net?] WARNING in bpf_lwt_seg6_adjust_srh

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: bf2468f9afba Merge branch 'locking-introduce-nested-bh-loc..
git tree: net-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13cb0aea980000
kernel config: https://syzkaller.appspot.com/x/.config?x=e78fc116033e0ab7
dashboard link: https://syzkaller.appspot.com/bug?extid=608a2acde8c5a101d07d
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12eaa3ea980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15eff72e980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f3b564f7e07c/disk-bf2468f9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cd47135279ed/vmlinux-bf2468f9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ccb81d174cf6/bzImage-bf2468f9.xz

The issue was bisected to:

commit d1542d4ae4dfdc47c9b3205ebe849ed23af213dd
Author: Sebastian Andrzej Siewior <big...@linutronix.de>
Date: Thu Jun 20 13:22:02 2024 +0000

seg6: Use nested-BH locking for seg6_bpf_srh_states.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10311e2a980000
final oops: https://syzkaller.appspot.com/x/report.txt?x=12311e2a980000
console output: https://syzkaller.appspot.com/x/log.txt?x=14311e2a980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+608a2a...@syzkaller.appspotmail.com
Fixes: d1542d4ae4df ("seg6: Use nested-BH locking for seg6_bpf_srh_states.")

------------[ cut here ]------------
WARNING: CPU: 0 PID: 5091 at net/core/filter.c:6579 ____bpf_lwt_seg6_adjust_srh net/core/filter.c:6579 [inline]
WARNING: CPU: 0 PID: 5091 at net/core/filter.c:6579 bpf_lwt_seg6_adjust_srh+0x877/0xb30 net/core/filter.c:6568
Modules linked in:
CPU: 0 PID: 5091 Comm: syz-executor570 Not tainted 6.10.0-rc4-syzkaller-00891-gbf2468f9afba #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
RIP: 0010:____bpf_lwt_seg6_adjust_srh net/core/filter.c:6579 [inline]
RIP: 0010:bpf_lwt_seg6_adjust_srh+0x877/0xb30 net/core/filter.c:6568
Code: bf 80 33 f8 eb 05 e8 b8 80 33 f8 48 c7 c0 f2 ff ff ff e9 d1 fc ff ff e8 a7 80 33 f8 48 63 c3 e9 c4 fc ff ff e8 9a 80 33 f8 90 <0f> 0b 90 4d 85 f6 0f 85 0e f9 ff ff e9 46 fa ff ff e8 83 80 33 f8
RSP: 0018:ffffc900034a77a0 EFLAGS: 00010293
RAX: ffffffff8962a486 RBX: 0000000000000000 RCX: ffff888017fdda00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900034a78d8 R08: ffffffff89629d8b R09: 1ffffffff1f5b52d
R10: dffffc0000000000 R11: ffffffffa00007d0 R12: 0000000000000000
R13: ffff8880b943d060 R14: 0000000000000000 R15: dffffc0000000000
FS: 000055555b006380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000564def260000 CR3: 00000000775ec000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
bpf_prog_2088341bddeddc1d+0x40/0x42
bpf_dispatcher_nop_func include/linux/bpf.h:1243 [inline]
__bpf_prog_run include/linux/filter.h:691 [inline]
bpf_prog_run include/linux/filter.h:698 [inline]
bpf_test_run+0x4f0/0xa90 net/bpf/test_run.c:432
bpf_prog_test_run_skb+0xafa/0x13b0 net/bpf/test_run.c:1081
bpf_prog_test_run+0x33a/0x3b0 kernel/bpf/syscall.c:4313
__sys_bpf+0x48d/0x810 kernel/bpf/syscall.c:5728
__do_sys_bpf kernel/bpf/syscall.c:5817 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5815 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5815
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f541c355529
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffca122c488 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007ffca122c658 RCX: 00007f541c355529
RDX: 0000000000000050 RSI: 00000000200002c0 RDI: 000000000000000a
RBP: 00007f541c3c8610 R08: 0000000000000000 R09: 00007ffca122c658
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffca122c648 R14: 0000000000000001 R15: 0000000000000001
</TASK>


---
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[Sebastian Andrzej Siewior]

On 2024-06-25 09:51:25 [-0700], syzbot wrote:
> Hello,
Hi,

…

> commit d1542d4ae4dfdc47c9b3205ebe849ed23af213dd
> Author: Sebastian Andrzej Siewior <big...@linutronix.de>
> Date: Thu Jun 20 13:22:02 2024 +0000
>
> seg6: Use nested-BH locking for seg6_bpf_srh_states.

…

> WARNING: CPU: 0 PID: 5091 at net/core/filter.c:6579 ____bpf_lwt_seg6_adjust_srh net/core/filter.c:6579 [inline]
> WARNING: CPU: 0 PID: 5091 at net/core/filter.c:6579 bpf_lwt_seg6_adjust_srh+0x877/0xb30 net/core/filter.c:6568

…

> Call Trace:
> <TASK>
> bpf_prog_2088341bddeddc1d+0x40/0x42
> bpf_dispatcher_nop_func include/linux/bpf.h:1243 [inline]
> __bpf_prog_run include/linux/filter.h:691 [inline]
> bpf_prog_run include/linux/filter.h:698 [inline]
> bpf_test_run+0x4f0/0xa90 net/bpf/test_run.c:432
> bpf_prog_test_run_skb+0xafa/0x13b0 net/bpf/test_run.c:1081
> bpf_prog_test_run+0x33a/0x3b0 kernel/bpf/syscall.c:4313
> __sys_bpf+0x48d/0x810 kernel/bpf/syscall.c:5728
> __do_sys_bpf kernel/bpf/syscall.c:5817 [inline]
> __se_sys_bpf kernel/bpf/syscall.c:5815 [inline]
> __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5815
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x77/0x7f

I assumed this can only originate from input_action_end_bpf() but
clearly this not a hard requirement based on the report.
So this a valid invocation and it should not have been killer earlier in
the stack?

Sebastian