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: 494d, last: 2d12h
▶ ▼ 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 (790):
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
2026/08/18 20:39 linux-6.1.y e4f7d8be268e 1e72964b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/05/07 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
2026/11/11 00:18 linux-6.1.y c75b0cf0982c d3056657 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/11/10 12:38 linux-6.1.y c75b0cf0982c 70ec0380 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/11/02 03:31 linux-6.1.y 08889840163e 25a0ae84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/11/02 02:18 linux-6.1.y 08889840163e 25a0ae84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/10/31 15:22 linux-6.1.y 08889840163e 2041d3f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/10/31 02:53 linux-6.1.y 08889840163e 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/10/23 01:40 linux-6.1.y 79807e970724 b55fad29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/10/17 19:01 linux-6.1.y 79807e970724 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/10/14 05:59 linux-6.1.y a500ba24937a 7321cd29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/10/10 16:49 linux-6.1.y a500ba24937a 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/10/03 18:10 linux-6.1.y a500ba24937a 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/10/02 09:12 linux-6.1.y 1a8763b93150 6d32eb1f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/09/27 04:43 linux-6.1.y 1a8763b93150 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/09/26 00:09 linux-6.1.y 1a8763b93150 f281d9d2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2026/09/19 09:22 linux-6.1.y 1a8763b93150 853b104b .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
2026/11/10 22:51 linux-6.1.y c75b0cf0982c d3056657 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/11/10 10:45 linux-6.1.y c75b0cf0982c 70ec0380 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/11/08 00:13 linux-6.1.y c75b0cf0982c 5cecaf1f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/11/06 11:43 linux-6.1.y 08889840163e 5cecaf1f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/11/02 01:14 linux-6.1.y 08889840163e 25a0ae84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/11/01 08:38 linux-6.1.y 08889840163e 25a0ae84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/11/01 08:38 linux-6.1.y 08889840163e 25a0ae84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/31 23:47 linux-6.1.y 08889840163e 2041d3f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/31 00:35 linux-6.1.y 08889840163e 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/27 13:19 linux-6.1.y 79807e970724 168cb7a2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/22 18:19 linux-6.1.y 79807e970724 b55fad29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/20 20:36 linux-6.1.y 79807e970724 df8746fb .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/20 20:34 linux-6.1.y 79807e970724 df8746fb .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/19 11:03 linux-6.1.y 79807e970724 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/17 11:22 linux-6.1.y 79807e970724 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/14 10:55 linux-6.1.y a500ba24937a 7321cd29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/14 04:55 linux-6.1.y a500ba24937a 7321cd29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/13 14:39 linux-6.1.y a500ba24937a 5a1eeac4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/13 14:39 linux-6.1.y a500ba24937a 5a1eeac4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/11 16:37 linux-6.1.y a500ba24937a 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/11 09:09 linux-6.1.y a500ba24937a 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/10 08:22 linux-6.1.y a500ba24937a 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/03 09:48 linux-6.1.y 1a8763b93150 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/10/02 00:21 linux-6.1.y 1a8763b93150 f5cdae2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/09/29 12:52 linux-6.1.y 1a8763b93150 7bf4ea23 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/09/26 22:49 linux-6.1.y 1a8763b93150 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/09/26 22:49 linux-6.1.y 1a8763b93150 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/09/26 19:10 linux-6.1.y 1a8763b93150 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/09/26 09:28 linux-6.1.y 1a8763b93150 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2026/09/20 08:56 linux-6.1.y 1a8763b93150 853b104b .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.