[v6.6] possible deadlock in smc_release

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0a805b6ea8cd Linux 6.6.116
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14b3c742580000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=65e45a84f76e6f44eaff
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/13874446b4b2/disk-0a805b6e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/69a5e59e1ade/vmlinux-0a805b6e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/322c0711f976/bzImage-0a805b6e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+65e45a...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.1542/9363 is trying to acquire lock:
ffff8880213d1458 ((work_completion)(&new_smc->smc_listen_work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
ffff8880213d1458 ((work_completion)(&new_smc->smc_listen_work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
ffff8880213d1458 ((work_completion)(&new_smc->smc_listen_work)){+.+.}-{0:0}, at: start_flush_work kernel/workqueue.c:3371 [inline]
ffff8880213d1458 ((work_completion)(&new_smc->smc_listen_work)){+.+.}-{0:0}, at: __flush_work+0xe6/0x9f0 kernel/workqueue.c:3429

but task is already holding lock:
ffff8880213d0130 (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:3532
smc_listen_out+0x109/0x3d0 net/smc/af_smc.c:1912
process_one_work kernel/workqueue.c:2634 [inline]
process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
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+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
touch_work_lockdep_map kernel/workqueue.c:3145 [inline]
start_flush_work kernel/workqueue.c:3397 [inline]
__flush_work+0x5ed/0x9f0 kernel/workqueue.c:3429
__cancel_work_timer+0x3b0/0x520 kernel/workqueue.c:3517
smc_clcsock_release+0x60/0xf0 net/smc/smc_close.c:29
__smc_release+0x661/0x7d0 net/smc/af_smc.c:301
smc_close_non_accepted+0xd5/0x1f0 net/smc/af_smc.c:1843
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:277
smc_release+0x2ce/0x530 net/smc/af_smc.c:344
__sock_release net/socket.c:659 [inline]
sock_close+0xbd/0x230 net/socket.c:1421
__fput+0x234/0x970 fs/file_table.c:384
task_work_run+0x1ce/0x250 kernel/task_work.c:239
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xf6/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
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.0.1542/9363:
#0: ffff88805b95be20 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
#0: ffff88805b95be20 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: __sock_release net/socket.c:658 [inline]
#0: ffff88805b95be20 (&sb->s_type->i_mutex_key#11){+.+.}-{3:3}, at: sock_close+0x9b/0x230 net/socket.c:1421
#1: ffff8880213d0130 (sk_lock-AF_SMC/1){+.+.}-{0:0}, at: smc_release+0x255/0x530 net/smc/af_smc.c:-1
#2: ffffffff8cd2fee0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#2: ffffffff8cd2fee0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#2: ffffffff8cd2fee0 (rcu_read_lock){....}-{1:2}, at: start_flush_work kernel/workqueue.c:3371 [inline]
#2: ffffffff8cd2fee0 (rcu_read_lock){....}-{1:2}, at: __flush_work+0xe6/0x9f0 kernel/workqueue.c:3429

stack backtrace:
CPU: 1 PID: 9363 Comm: syz.0.1542 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
<TASK>
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
check_noncircular+0x2bd/0x3c0 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+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
touch_work_lockdep_map kernel/workqueue.c:3145 [inline]
start_flush_work kernel/workqueue.c:3397 [inline]
__flush_work+0x5ed/0x9f0 kernel/workqueue.c:3429
__cancel_work_timer+0x3b0/0x520 kernel/workqueue.c:3517
smc_clcsock_release+0x60/0xf0 net/smc/smc_close.c:29
__smc_release+0x661/0x7d0 net/smc/af_smc.c:301
smc_close_non_accepted+0xd5/0x1f0 net/smc/af_smc.c:1843
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:277
smc_release+0x2ce/0x530 net/smc/af_smc.c:344
__sock_release net/socket.c:659 [inline]
sock_close+0xbd/0x230 net/socket.c:1421
__fput+0x234/0x970 fs/file_table.c:384
task_work_run+0x1ce/0x250 kernel/task_work.c:239
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xf6/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f00a4b8f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f00a5943038 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f00a4de5fa0 RCX: 00007f00a4b8f749
RDX: 0000000000000000 RSI: ffffffffffffffff RDI: 0000000000000000
RBP: 00007f00a4c13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f00a4de6038 R14: 00007f00a4de5fa0 R15: 00007ffe0417a9d8
</TASK>


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