possible deadlock in unix_collect_skb

Status: upstream: reported C repro on 2025/07/06 13:45
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+935eda0926f44898461e@syzkaller.appspotmail.com
First crash: 384d, last: 8h44m
Bug presence (2)
Date Name Commit Repro Result
2026/01/25 linux-6.1.y (ToT) cd9b81672742 C [report] possible deadlock in unix_collect_skb
2026/01/25 upstream (ToT) 913fb068e259 C Didn't crash
Fix bisection attempts (6)
Created Duration User Patch Repo Result
2026/05/11 11:20 15m fix candidate upstream error job log
2026/03/28 12:38 14m fix candidate upstream error job log
2026/02/25 20:33 1m fix candidate upstream error job log
2026/01/25 19:38 1m fix candidate upstream error job log
2025/09/27 23:42 2h49m fix candidate upstream OK (0) job log
2025/07/25 07:11 16m fix candidate upstream error job log

Sample crash report:
IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
kworker/u4:4/75 is trying to acquire lock:
ffff88801e7299e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff88801e7299e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: unix_collect_skb+0x15a/0x550 net/unix/garbage.c:363

but task is already holding lock:
ffff88801e7289e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff88801e7289e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: unix_collect_skb+0xb7/0x550 net/unix/garbage.c:355

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(rlock-AF_UNIX);
  lock(rlock-AF_UNIX);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

4 locks held by kworker/u4:4/75:
 #0: ffff888017479138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #1: ffffc90001597d00 (unix_gc_work){+.+.}-{0:0}, at: process_one_work+0x7b0/0x1160 kernel/workqueue.c:2267
 #2: ffffffff8de46078 (unix_gc_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #2: ffffffff8de46078 (unix_gc_lock){+.+.}-{2:2}, at: __unix_gc+0xc4/0x19b0 net/unix/garbage.c:563
 #3: ffff88801e7289e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #3: ffff88801e7289e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: unix_collect_skb+0xb7/0x550 net/unix/garbage.c:355

stack backtrace:
CPU: 0 PID: 75 Comm: kworker/u4:4 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events_unbound __unix_gc
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 __lock_acquire+0x123e/0x7d10 kernel/locking/lockdep.c:-1
 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:351 [inline]
 unix_collect_skb+0x15a/0x550 net/unix/garbage.c:363
 __unix_walk_scc net/unix/garbage.c:486 [inline]
 unix_walk_scc net/unix/garbage.c:517 [inline]
 __unix_gc+0x1107/0x19b0 net/unix/garbage.c:575
 process_one_work+0x8a2/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1270 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>

Crashes (643):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/25 15:40 linux-6.1.y cd9b81672742 40acda8a .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/05/07 18:21 linux-6.1.y 4931e0e1673d cbf9e0fc .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/10/17 08:58 linux-6.1.y c2fda4b3f577 19568248 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/07/06 22:56 linux-6.1.y 04d1ccaa9c28 4f67c4ae .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/25 17:32 linux-6.1.y dc5c83b7f5f8 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/25 01:26 linux-6.1.y dc5c83b7f5f8 dd737a83 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/20 23:17 linux-6.1.y 090666d3cc90 de6a700d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/18 14:59 linux-6.1.y 090666d3cc90 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/16 09:21 linux-6.1.y 090666d3cc90 27a8bd60 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/16 09:21 linux-6.1.y 090666d3cc90 27a8bd60 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/12 17:07 linux-6.1.y 090666d3cc90 d78ea535 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/10 05:56 linux-6.1.y 090666d3cc90 4167ee25 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/04 06:54 linux-6.1.y fdb6fcb41cc7 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/04 04:34 linux-6.1.y fdb6fcb41cc7 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/04 04:34 linux-6.1.y fdb6fcb41cc7 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/04 01:37 linux-6.1.y fdb6fcb41cc7 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/04 00:08 linux-6.1.y fdb6fcb41cc7 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/03 20:09 linux-6.1.y fdb6fcb41cc7 58bf2096 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/03 15:43 linux-6.1.y fdb6fcb41cc7 58bf2096 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/03 15:40 linux-6.1.y fdb6fcb41cc7 58bf2096 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/03 13:14 linux-6.1.y fdb6fcb41cc7 58bf2096 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/03 01:42 linux-6.1.y fdb6fcb41cc7 2b70b115 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/02 08:02 linux-6.1.y fdb6fcb41cc7 27192279 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/02 04:40 linux-6.1.y fdb6fcb41cc7 27192279 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/02 03:33 linux-6.1.y fdb6fcb41cc7 27192279 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/01 15:58 linux-6.1.y fdb6fcb41cc7 00a5cf1c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/06/13 15:37 linux-6.1.y 228da13e907e 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/06/13 05:02 linux-6.1.y 228da13e907e 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/07/06 13:45 linux-6.1.y 04d1ccaa9c28 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/07/25 12:48 linux-6.1.y dc5c83b7f5f8 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/25 12:46 linux-6.1.y dc5c83b7f5f8 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/24 22:23 linux-6.1.y dc5c83b7f5f8 dd737a83 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/22 21:26 linux-6.1.y 090666d3cc90 4a865b71 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/20 19:16 linux-6.1.y 090666d3cc90 de6a700d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/19 23:56 linux-6.1.y 090666d3cc90 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/16 05:23 linux-6.1.y 090666d3cc90 27a8bd60 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/13 21:06 linux-6.1.y 090666d3cc90 cc4833d0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/12 13:41 linux-6.1.y 090666d3cc90 d78ea535 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/04 02:50 linux-6.1.y fdb6fcb41cc7 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/03 14:39 linux-6.1.y fdb6fcb41cc7 58bf2096 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/03 11:47 linux-6.1.y fdb6fcb41cc7 58bf2096 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/03 10:34 linux-6.1.y fdb6fcb41cc7 58bf2096 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/03 00:22 linux-6.1.y fdb6fcb41cc7 2b70b115 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/01 23:39 linux-6.1.y fdb6fcb41cc7 27192279 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/07/01 09:57 linux-6.1.y fdb6fcb41cc7 00a5cf1c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/06/28 07:23 linux-6.1.y fdb6fcb41cc7 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/06/13 13:00 linux-6.1.y 228da13e907e 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/06/12 23:47 linux-6.1.y 228da13e907e 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/05/31 20:56 linux-6.1.y dcbcab9d7079 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
* Struck through repros no longer work on HEAD.