syzbot


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: 104d, last: 19h40m
Bug presence (2)
Date Name Commit Repro Result
2025/07/07 linux-6.1.y (ToT) 04d1ccaa9c28 C [report] possible deadlock in unix_collect_skb
2025/07/07 upstream (ToT) d7b8f8e20813 C Didn't crash
Fix bisection attempts (2)
Created Duration User Patch Repo Result
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): wlan1: link becomes ready
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
kworker/u4:6/4424 is trying to acquire lock:
ffff0000d4bf21e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff0000d4bf21e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: unix_collect_skb+0x140/0x480 net/unix/garbage.c:361

but task is already holding lock:
ffff0000d4bf11e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff0000d4bf11e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: unix_collect_skb+0xa8/0x480 net/unix/garbage.c:353

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/u4:6/4424:
 #0: ffff0000c0029138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x6b4/0x13a8 kernel/workqueue.c:2265
 #1: ffff800020c17c20 (unix_gc_work){+.+.}-{0:0}, at: process_one_work+0x6f8/0x13a8 kernel/workqueue.c:2267
 #2: ffff800017829458 (unix_gc_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #2: ffff800017829458 (unix_gc_lock){+.+.}-{2:2}, at: __unix_gc+0xb8/0x1334 net/unix/garbage.c:555
 #3: ffff0000d4bf11e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #3: ffff0000d4bf11e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: unix_collect_skb+0xa8/0x480 net/unix/garbage.c:353

stack backtrace:
CPU: 1 PID: 4424 Comm: kworker/u4:6 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
Workqueue: events_unbound __unix_gc
Call trace:
 dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 __lock_acquire+0x18b4/0x6544 kernel/locking/lockdep.c:-1
 lock_acquire+0x20c/0x644 kernel/locking/lockdep.c:5662
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x54/0x6c kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:351 [inline]
 unix_collect_skb+0x140/0x480 net/unix/garbage.c:361
 __unix_walk_scc net/unix/garbage.c:484 [inline]
 unix_walk_scc net/unix/garbage.c:509 [inline]
 __unix_gc+0xd18/0x1334 net/unix/garbage.c:567
 process_one_work+0x7f4/0x13a8 kernel/workqueue.c:2292
 worker_thread+0x8c8/0xfbc kernel/workqueue.c:2439
 kthread+0x250/0x2d8 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

Crashes (142):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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
2025/10/18 07:54 linux-6.1.y c2fda4b3f577 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/10/18 07:54 linux-6.1.y c2fda4b3f577 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/10/17 18:01 linux-6.1.y c2fda4b3f577 7adf5298 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/10/05 09:25 linux-6.1.y 882efbdd9d34 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/10/03 13:32 linux-6.1.y 882efbdd9d34 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/09/30 00:51 linux-6.1.y 7b34dc04e4ff 86341da6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/09/25 22:13 linux-6.1.y 7b34dc04e4ff 0abd0691 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/09/12 21:39 linux-6.1.y 3db754f56897 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/09/10 19:50 linux-6.1.y f97f1002271b fdeaa69b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/09/06 16:30 linux-6.1.y 28c695c365e1 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/09/03 18:39 linux-6.1.y f89b6e15694c 96a211bc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/09/01 01:26 linux-6.1.y f89b6e15694c 807a3b61 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/08/21 06:00 linux-6.1.y 0bc96de781b4 0b9605c8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in unix_collect_skb
2025/08/10 00:15 linux-6.1.y 3594f306da12 32a0e5ed .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
2025/10/17 08:02 linux-6.1.y c2fda4b3f577 19568248 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/10/05 06:04 linux-6.1.y 882efbdd9d34 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/10/04 08:54 linux-6.1.y 882efbdd9d34 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/10/03 07:56 linux-6.1.y 882efbdd9d34 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/10/03 02:41 linux-6.1.y 882efbdd9d34 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/10/02 23:30 linux-6.1.y 882efbdd9d34 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/09/25 20:52 linux-6.1.y 7b34dc04e4ff 0abd0691 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/09/18 23:56 linux-6.1.y 3db754f56897 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/09/10 14:14 linux-6.1.y f97f1002271b fdeaa69b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/09/07 07:04 linux-6.1.y 28c695c365e1 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/09/07 05:10 linux-6.1.y 28c695c365e1 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/09/06 15:13 linux-6.1.y 28c695c365e1 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/09/06 14:38 linux-6.1.y 28c695c365e1 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/09/03 10:50 linux-6.1.y f89b6e15694c 96a211bc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/09/01 02:42 linux-6.1.y f89b6e15694c 807a3b61 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/08/31 23:22 linux-6.1.y f89b6e15694c 807a3b61 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/08/29 17:55 linux-6.1.y f89b6e15694c 3e1beec6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/08/29 05:06 linux-6.1.y f89b6e15694c d401b9d7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/08/27 18:55 linux-6.1.y 0bc96de781b4 e12e5ba4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/08/20 23:53 linux-6.1.y 0bc96de781b4 0b9605c8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/08/11 05:26 linux-6.1.y 3594f306da12 32a0e5ed .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/08/11 05:24 linux-6.1.y 3594f306da12 32a0e5ed .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/08/09 23:21 linux-6.1.y 3594f306da12 32a0e5ed .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/08/09 23:21 linux-6.1.y 3594f306da12 32a0e5ed .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/08/09 19:32 linux-6.1.y 3594f306da12 32a0e5ed .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/08/06 11:11 linux-6.1.y 3594f306da12 ffe1dd46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/08/06 11:10 linux-6.1.y 3594f306da12 ffe1dd46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in unix_collect_skb
2025/08/04 09:08 linux-6.1.y 3594f306da12 7368264b .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.