linux-kernel - Re: [syzbot] [bpf?] [net?] WARNING in sock_map_delete

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Message-ID: <20251011234106.8522-1-hdanton@sina.com>
Date: Sun, 12 Oct 2025 07:41:05 +0800
From: Hillf Danton <hdanton@...a.com>
To: ast@...nel.org,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: syzbot <syzbot+ad76dbe500667f3a4e17@...kaller.appspotmail.com>,
	bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bpf?] [net?] WARNING in sock_map_delete_elem (2)

On Fri, 10 Oct 2025 08:41:28 -0700
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    fd94619c4336 Merge tag 'zonefs-6.18-rc1' of git://git.kern..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14ff8ee2580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e2b03b8b7809165e
> dashboard link: https://syzkaller.appspot.com/bug?extid=ad76dbe500667f3a4e17
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/201636e25a0b/disk-fd94619c.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/b63e3832240c/vmlinux-fd94619c.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/11fc378734e8/bzImage-fd94619c.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+ad76dbe500667f3a4e17@...kaller.appspotmail.com
> 
> ------------[ cut here ]------------
> DEBUG_LOCKS_WARN_ON(this_cpu_read(softirq_ctrl.cnt))

Did bpf help find out anything wrong in softirq?

> WARNING: CPU: 0 PID: 5969 at kernel/softirq.c:176 __local_bh_disable_ip+0x3d9/0x540 kernel/softirq.c:176
> Modules linked in:
> CPU: 0 UID: 0 PID: 5969 Comm: syz.1.2 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
> RIP: 0010:__local_bh_disable_ip+0x3d9/0x540 kernel/softirq.c:176
> Code: 0f b6 04 28 84 c0 0f 85 56 01 00 00 83 3d 52 9b 32 0d 00 75 19 90 48 c7 c7 c0 b7 c9 8a 48 c7 c6 00 b8 c9 8a e8 f8 5f fe ff 90 <0f> 0b 90 90 90 e9 7b ff ff ff 90 0f 0b 90 e9 71 fe ff ff e8 cf 84
> RSP: 0018:ffffc900056bf940 EFLAGS: 00010246
> RAX: f63c8546519c3800 RBX: 1ffff92000ad7f30 RCX: 0000000000080000
> RDX: ffffc9000d891000 RSI: 00000000000093ed RDI: 00000000000093ee
> RBP: ffffc900056bfa48 R08: 0000000000000000 R09: 0000000000000000
> R10: dffffc0000000000 R11: ffffed101710487b R12: ffff88803c911e00
> R13: dffffc0000000000 R14: ffff88803c91294c R15: 1ffff11007922529
> FS:  00007fe7c46d66c0(0000) GS:ffff888127020000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000001b30217ff8 CR3: 000000001dfd6000 CR4: 00000000003526f0
> Call Trace:
>  <TASK>
>  local_bh_disable include/linux/bottom_half.h:20 [inline]
>  spin_lock_bh include/linux/spinlock_rt.h:87 [inline]
>  __sock_map_delete net/core/sock_map.c:421 [inline]
>  sock_map_delete_elem+0xaf/0x170 net/core/sock_map.c:452
>  bpf_prog_e78d8a1634f5e22d+0x46/0x4e
>  bpf_dispatcher_nop_func include/linux/bpf.h:1350 [inline]
>  __bpf_prog_run include/linux/filter.h:721 [inline]
>  bpf_prog_run include/linux/filter.h:728 [inline]
>  bpf_prog_run_pin_on_cpu include/linux/filter.h:745 [inline]
>  bpf_flow_dissect+0x225/0x720 net/core/flow_dissector.c:1024
>  bpf_prog_test_run_flow_dissector+0x37c/0x5c0 net/bpf/test_run.c:1425
>  bpf_prog_test_run+0x2cd/0x340 kernel/bpf/syscall.c:4673
>  __sys_bpf+0x562/0x860 kernel/bpf/syscall.c:6152
>  __do_sys_bpf kernel/bpf/syscall.c:6244 [inline]
>  __se_sys_bpf kernel/bpf/syscall.c:6242 [inline]
>  __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6242
>  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