syzbot


possible deadlock in smc_release (2)

Status: upstream: reported on 2026/05/22 12:09
Reported-by: syzbot+df885f0959236be11223@syzkaller.appspotmail.com
First crash: 4d19h, last: 4d19h
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 possible deadlock in smc_release 4 1 188d 188d 0/2 auto-obsoleted due to no activity on 2026/02/27 23:52
linux-5.15 possible deadlock in smc_release missing-backport origin:lts-only 4 C error 1044 4h48m 610d 0/3 upstream: reported C repro on 2024/09/24 05:56
upstream possible deadlock in smc_release smc 4 C error 522 3h35m 844d 0/29 upstream: reported C repro on 2024/02/02 13:26
linux-6.1 possible deadlock in smc_release origin:upstream missing-backport 4 C 1560 4h45m 848d 0/3 upstream: reported C repro on 2024/01/29 16:17

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.3071/17280 is trying to acquire lock:
ffff88807a861f98 ((work_completion)(&new_smc->smc_listen_work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
ffff88807a861f98 ((work_completion)(&new_smc->smc_listen_work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
ffff88807a861f98 ((work_completion)(&new_smc->smc_listen_work)){+.+.}-{0:0}, at: start_flush_work kernel/workqueue.c:3412 [inline]
ffff88807a861f98 ((work_completion)(&new_smc->smc_listen_work)){+.+.}-{0:0}, at: __flush_work+0x118/0xaa0 kernel/workqueue.c:3470

but task is already holding lock:
ffff88807a860c70 (sk_lock-AF_SMC/1){+.+.}-{0:0}, at: smc_release+0x255/0x530 net/smc/af_smc.c:-1

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (sk_lock-AF_SMC/1){+.+.}-{0:0}:
       lock_sock_nested+0x48/0x100 net/core/sock.c:3535
       smc_listen_out+0x109/0x3d0 net/smc/af_smc.c:1922
       smc_listen_out_connected net/smc/af_smc.c:1942 [inline]
       smc_listen_decline net/smc/af_smc.c:1977 [inline]
       smc_listen_work+0x581/0xf40 net/smc/af_smc.c:2574
       process_one_work kernel/workqueue.c:2653 [inline]
       process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
       worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
       kthread+0x2fa/0x390 kernel/kthread.c:388
       ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

-> #0 ((work_completion)(&new_smc->smc_listen_work)){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x2df1/0x7d40 kernel/locking/lockdep.c:5137
       lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
       touch_work_lockdep_map kernel/workqueue.c:3186 [inline]
       start_flush_work kernel/workqueue.c:3438 [inline]
       __flush_work+0x64e/0xaa0 kernel/workqueue.c:3470
       __cancel_work_timer+0x3f8/0x560 kernel/workqueue.c:3558
       smc_clcsock_release+0x60/0xf0 net/smc/smc_close.c:29
       __smc_release+0x661/0x7d0 net/smc/af_smc.c:311
       smc_close_non_accepted+0xd5/0x1f0 net/smc/af_smc.c:1853
       smc_close_cleanup_listen net/smc/smc_close.c:45 [inline]
       smc_close_active+0xb61/0xf00 net/smc/smc_close.c:225
       __smc_release+0x8d/0x7d0 net/smc/af_smc.c:287
       smc_release+0x2ce/0x530 net/smc/af_smc.c:354
       __sock_release net/socket.c:659 [inline]
       sock_close+0xbd/0x230 net/socket.c:1420
       __fput+0x234/0x970 fs/file_table.c:384
       __do_sys_close fs/open.c:1573 [inline]
       __se_sys_close+0x15f/0x220 fs/open.c:1558
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sk_lock-AF_SMC/1);
                               lock((work_completion)(&new_smc->smc_listen_work));
                               lock(sk_lock-AF_SMC/1);
  lock((work_completion)(&new_smc->smc_listen_work));

 *** DEADLOCK ***

3 locks held by syz.2.3071/17280:
 #0: ffff88805e189420 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
 #0: ffff88805e189420 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: __sock_release net/socket.c:658 [inline]
 #0: ffff88805e189420 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: sock_close+0x9b/0x230 net/socket.c:1420
 #1: ffff88807a860c70 (sk_lock-AF_SMC/1){+.+.}-{0:0}, at: smc_release+0x255/0x530 net/smc/af_smc.c:-1
 #2: ffffffff8d132160 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #2: ffffffff8d132160 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #2: ffffffff8d132160 (rcu_read_lock){....}-{1:2}, at: start_flush_work kernel/workqueue.c:3412 [inline]
 #2: ffffffff8d132160 (rcu_read_lock){....}-{1:2}, at: __flush_work+0x118/0xaa0 kernel/workqueue.c:3470

stack backtrace:
CPU: 0 PID: 17280 Comm: syz.2.3071 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 check_noncircular+0x2fc/0x400 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x2df1/0x7d40 kernel/locking/lockdep.c:5137
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
 touch_work_lockdep_map kernel/workqueue.c:3186 [inline]
 start_flush_work kernel/workqueue.c:3438 [inline]
 __flush_work+0x64e/0xaa0 kernel/workqueue.c:3470
 __cancel_work_timer+0x3f8/0x560 kernel/workqueue.c:3558
 smc_clcsock_release+0x60/0xf0 net/smc/smc_close.c:29
 __smc_release+0x661/0x7d0 net/smc/af_smc.c:311
 smc_close_non_accepted+0xd5/0x1f0 net/smc/af_smc.c:1853
 smc_close_cleanup_listen net/smc/smc_close.c:45 [inline]
 smc_close_active+0xb61/0xf00 net/smc/smc_close.c:225
 __smc_release+0x8d/0x7d0 net/smc/af_smc.c:287
 smc_release+0x2ce/0x530 net/smc/af_smc.c:354
 __sock_release net/socket.c:659 [inline]
 sock_close+0xbd/0x230 net/socket.c:1420
 __fput+0x234/0x970 fs/file_table.c:384
 __do_sys_close fs/open.c:1573 [inline]
 __se_sys_close+0x15f/0x220 fs/open.c:1558
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb4c2f9ce59
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:00007fb4c3e66028 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 00007fb4c3215fa0 RCX: 00007fb4c2f9ce59
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007fb4c3032d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb4c3216038 R14: 00007fb4c3215fa0 R15: 00007ffe7e105a98
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/22 12:08 linux-6.6.y eac8889a3a1c 70ae9b03 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in smc_release
* Struck through repros no longer work on HEAD.