possible deadlock in __smc_lgr_terminate

Status: upstream: reported on 2026/10/25 00:35
Subsystems: smc
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+7ea1f5efd5de7e24f1de@syzkaller.appspotmail.com
First crash: 4d01h, last: 4d01h
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
81568629 repro-c 💥 possible deadlock in __smc_lgr_terminate 2026/10/23 14:08 2026/10/23 14:08 2026/10/24 02:02 1d9ca40b
4bb543c8 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ✅ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ possible deadlock in __smc_lgr_terminate 2026/10/22 01:07 2026/10/22 01:07 2026/10/22 02:00 42e06812
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [smc?] possible deadlock in __smc_lgr_terminate 0 (1) 2026/10/25 00:35

Sample crash report:
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
kworker/0:2/7972 is trying to acquire lock:
ffff8880419c3118 (sk_lock-AF_SMC){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1715 [inline]
ffff8880419c3118 (sk_lock-AF_SMC){+.+.}-{0:0}, at: __smc_lgr_terminate+0x19e/0x6a0 net/smc/smc_core.c:1580

but task is already holding lock:
ffff8880326f9298 (sk_lock-AF_SMC){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1715 [inline]
ffff8880326f9298 (sk_lock-AF_SMC){+.+.}-{0:0}, at: smc_listen_work+0x5e/0x1410 net/smc/af_smc.c:2463

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

       CPU0
       ----
  lock(sk_lock-AF_SMC);
  lock(sk_lock-AF_SMC);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

locks held by kworker/0:2/7972: 3, last CPU#0:
 #0: ffff8880344a4938 ((wq_completion)smc_hs_wq){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffff8880344a4938 ((wq_completion)smc_hs_wq){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffff8880344a4938 ((wq_completion)smc_hs_wq){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #0: ffff8880344a4938 ((wq_completion)smc_hs_wq){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
 #1: ffffc900045ffc40 ((work_completion)(&new_smc->smc_listen_work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #1: ffffc900045ffc40 ((work_completion)(&new_smc->smc_listen_work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #1: ffffc900045ffc40 ((work_completion)(&new_smc->smc_listen_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #1: ffffc900045ffc40 ((work_completion)(&new_smc->smc_listen_work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
 #2: ffff8880326f9298 (sk_lock-AF_SMC){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1715 [inline]
 #2: ffff8880326f9298 (sk_lock-AF_SMC){+.+.}-{0:0}, at: smc_listen_work+0x5e/0x1410 net/smc/af_smc.c:2463

stack backtrace:
CPU: 0 UID: 0 PID: 7972 Comm: kworker/0:2 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Workqueue: smc_hs_wq smc_listen_work
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_deadlock_bug+0x27a/0x290 kernel/locking/lockdep.c:3085
 check_deadlock kernel/locking/lockdep.c:3137 [inline]
 validate_chain kernel/locking/lockdep.c:3939 [inline]
 __lock_acquire+0x25db/0x2de0 kernel/locking/lockdep.c:5288
 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
 lock_sock_nested+0x41/0x130 net/core/sock.c:3865
 lock_sock include/net/sock.h:1715 [inline]
 __smc_lgr_terminate+0x19e/0x6a0 net/smc/smc_core.c:1580
 smc_conn_abort net/smc/af_smc.c:1019 [inline]
 smc_listen_decline net/smc/af_smc.c:1978 [inline]
 smc_listen_work+0x69e/0x1410 net/smc/af_smc.c:2588
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
 kthread+0x38b/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/21 00:33 upstream f47d223627f8 df8746fb .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root possible deadlock in __smc_lgr_terminate
* Struck through repros no longer work on HEAD.