Subject: [syzbot] [net?] BUG: spinlock already unlocked in lec_atm_close

From: syzbot <[email-masked]>
Date: Tue, 21 Apr 2026 08:35:31 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    1f5ffc672165 Fix mismerge of the arm64 / timer-core interr..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12b85906580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=95729ed00549063a
dashboard link: https://syzkaller.appspot.com/bug?extid=49a9c7b281bb147f8eb3
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6b552538b97f/disk-1f5ffc67.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/724a3a1d69d7/vmlinux-1f5ffc67.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ea684969e2c2/bzImage-1f5ffc67.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

BUG: spinlock already unlocked on CPU#0, syz.2.25/6044
 lock: 0xffff888032ea0ea0, .magic: dead4ead, .owner: <none>/-1, .owner_cpu: -1
CPU: 0 UID: 0 PID: 6044 Comm: syz.2.25 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 spin_bug kernel/locking/spinlock_debug.c:78 [inline]
 debug_spin_unlock kernel/locking/spinlock_debug.c:101 [inline]
 do_raw_spin_unlock+0x143/0x210 kernel/locking/spinlock_debug.c:141
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:177 [inline]
 _raw_spin_unlock_irqrestore+0x23/0x80 kernel/locking/spinlock.c:198
 spin_unlock_irqrestore include/linux/spinlock.h:408 [inline]
 lec_arp_destroy net/atm/lec.c:1543 [inline]
 lec_atm_close+0x976/0x9e0 net/atm/lec.c:497
 vcc_destroy_socket net/atm/common.c:181 [inline]
 vcc_release+0x10f/0x580 net/atm/common.c:205
 svc_release+0x6c/0xd0 net/atm/svc.c:95
 __sock_release net/socket.c:722 [inline]
 sock_close+0xc3/0x240 net/socket.c:1514
 __fput+0x44f/0xa60 fs/file_table.c:510
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 get_signal+0x11eb/0x1330 kernel/signal.c:2811
 arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:328 [inline]
 do_syscall_64+0x33e/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1af9f9c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1afae30028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: 0000000000000000 RBX: 00007f1afa215fa0 RCX: 00007f1af9f9c819
RDX: 0000000000000000 RSI: 00000000000061d0 RDI: 0000000000000005
RBP: 00007f1afa032c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1afa216038 R14: 00007f1afa215fa0 R15: 00007ffdc6f7add8
 </TASK>
------------[ cut here ]------------
pvqspinlock: lock 0xffff888032ea0ea0 has corrupted value 0x0!
WARNING: kernel/locking/qspinlock_paravirt.h:506 at __pv_queued_spin_unlock_slowpath+0x1a5/0x270 kernel/locking/qspinlock_paravirt.h:504, CPU#0: syz.2.25/6044
Modules linked in:
CPU: 0 UID: 0 PID: 6044 Comm: syz.2.25 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:__pv_queued_spin_unlock_slowpath+0x1ce/0x270 kernel/locking/qspinlock_paravirt.h:504
Code: 04 48 89 df be 04 00 00 00 e8 4e 58 7b f6 48 89 d8 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 87 00 00 00 8b 13 4c 89 f7 48 89 de <67> 48 0f b9 3a eb 98 48 c7 c7 30 c8 82 8e 4c 89 f6 4c 89 fa e8 f9
RSP: 0018:ffffc90005087920 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff888032ea0ea0 RCX: ffffffff8bb5d542
RDX: 0000000000000000 RSI: ffff888032ea0ea0 RDI: ffffffff90357220
RBP: 1ffff110065d41d5 R08: ffff888032ea0ea3 R09: 1ffff110065d41d4
R10: dffffc0000000000 R11: ffffed10065d41d5 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffffff90357220 R15: ffff888032ea0ea8
FS:  00007f1afae306c0(0000) GS:ffff888125245000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1994be92f8 CR3: 000000007abce000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __raw_callee_save___pv_queued_spin_unlock_slowpath+0x15/0x30
 .slowpath+0x9/0x18
 pv_queued_spin_unlock arch/x86/include/asm/paravirt-spinlock.h:40 [inline]
 queued_spin_unlock arch/x86/include/asm/paravirt-spinlock.h:72 [inline]
 do_raw_spin_unlock+0xf5/0x210 kernel/locking/spinlock_debug.c:142
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:177 [inline]
 _raw_spin_unlock_irqrestore+0x23/0x80 kernel/locking/spinlock.c:198
 spin_unlock_irqrestore include/linux/spinlock.h:408 [inline]
 lec_arp_destroy net/atm/lec.c:1543 [inline]
 lec_atm_close+0x976/0x9e0 net/atm/lec.c:497
 vcc_destroy_socket net/atm/common.c:181 [inline]
 vcc_release+0x10f/0x580 net/atm/common.c:205
 svc_release+0x6c/0xd0 net/atm/svc.c:95
 __sock_release net/socket.c:722 [inline]
 sock_close+0xc3/0x240 net/socket.c:1514
 __fput+0x44f/0xa60 fs/file_table.c:510
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 get_signal+0x11eb/0x1330 kernel/signal.c:2811
 arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:328 [inline]
 do_syscall_64+0x33e/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1af9f9c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1afae30028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: 0000000000000000 RBX: 00007f1afa215fa0 RCX: 00007f1af9f9c819
RDX: 0000000000000000 RSI: 00000000000061d0 RDI: 0000000000000005
RBP: 00007f1afa032c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1afa216038 R14: 00007f1afa215fa0 R15: 00007ffdc6f7add8
 </TASK>
----------------
Code disassembly (best guess):
   0:	04 48                	add    $0x48,%al
   2:	89 df                	mov    %ebx,%edi
   4:	be 04 00 00 00       	mov    $0x4,%esi
   9:	e8 4e 58 7b f6       	call   0xf67b585c
   e:	48 89 d8             	mov    %rbx,%rax
  11:	48 c1 e8 03          	shr    $0x3,%rax
  15:	42 0f b6 04 28       	movzbl (%rax,%r13,1),%eax
  1a:	84 c0                	test   %al,%al
  1c:	0f 85 87 00 00 00    	jne    0xa9
  22:	8b 13                	mov    (%rbx),%edx
  24:	4c 89 f7             	mov    %r14,%rdi
  27:	48 89 de             	mov    %rbx,%rsi
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	eb 98                	jmp    0xffffffc9
  31:	48 c7 c7 30 c8 82 8e 	mov    $0xffffffff8e82c830,%rdi
  38:	4c 89 f6             	mov    %r14,%rsi
  3b:	4c 89 fa             	mov    %r15,%rdx
  3e:	e8                   	.byte 0xe8
  3f:	f9                   	stc

---
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