syzbot

======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc2-syzkaller-00087-gcfb2e2c57aef #0 Tainted: G     U             
------------------------------------------------------
kworker/1:4/5883 is trying to acquire lock:
ffffffff9012e7e8 (rtnl_mutex){+.+.}-{4:4}, at: smc_vlan_by_tcpsk+0x251/0x620 net/smc/smc_core.c:1908

but task is already holding lock:
ffff88807d8fc758 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1651 [inline]
ffff88807d8fc758 (sk_lock-AF_INET){+.+.}-{0:0}, at: smc_connect_work+0x53a/0xae0 net/smc/af_smc.c:1600

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (sk_lock-AF_INET){+.+.}-{0:0}:
       lock_sock_nested+0x41/0xf0 net/core/sock.c:3702
       lock_sock include/net/sock.h:1651 [inline]
       sockopt_lock_sock net/core/sock.c:1148 [inline]
       sockopt_lock_sock+0x54/0x70 net/core/sock.c:1139
       do_ip_setsockopt+0xfe/0x3240 net/ipv4/ip_sockglue.c:1078
       ip_setsockopt+0x59/0xf0 net/ipv4/ip_sockglue.c:1417
       udp_setsockopt+0x7d/0xd0 net/ipv4/udp.c:3058
       do_sock_setsockopt+0x221/0x470 net/socket.c:2296
       __sys_setsockopt+0x1a0/0x230 net/socket.c:2321
       __do_sys_setsockopt net/socket.c:2327 [inline]
       __se_sys_setsockopt net/socket.c:2324 [inline]
       __x64_sys_setsockopt+0xbd/0x160 net/socket.c:2324
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (rtnl_mutex){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3166 [inline]
       check_prevs_add kernel/locking/lockdep.c:3285 [inline]
       validate_chain kernel/locking/lockdep.c:3909 [inline]
       __lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235
       lock_acquire kernel/locking/lockdep.c:5866 [inline]
       lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
       smc_vlan_by_tcpsk+0x251/0x620 net/smc/smc_core.c:1908
       __smc_connect+0x44b/0x4880 net/smc/af_smc.c:1520
       smc_connect_work+0x54c/0xae0 net/smc/af_smc.c:1613
       process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3238
       process_scheduled_works kernel/workqueue.c:3319 [inline]
       worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
       kthread+0x3c2/0x780 kernel/kthread.c:464
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sk_lock-AF_INET);
                               lock(rtnl_mutex);
                               lock(sk_lock-AF_INET);
  lock(rtnl_mutex);

 *** DEADLOCK ***

3 locks held by kworker/1:4/5883:
 #0: ffff888031e09548 ((wq_completion)smc_hs_wq){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc900049cfd18 ((work_completion)(&smc->connect_work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
 #2: ffff88807d8fc758 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1651 [inline]
 #2: ffff88807d8fc758 (sk_lock-AF_INET){+.+.}-{0:0}, at: smc_connect_work+0x53a/0xae0 net/smc/af_smc.c:1600

stack backtrace:
CPU: 1 UID: 0 PID: 5883 Comm: kworker/1:4 Tainted: G     U              6.15.0-rc2-syzkaller-00087-gcfb2e2c57aef #0 PREEMPT(full) 
Tainted: [U]=USER
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: smc_hs_wq smc_connect_work
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2079
 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2211
 check_prev_add kernel/locking/lockdep.c:3166 [inline]
 check_prevs_add kernel/locking/lockdep.c:3285 [inline]
 validate_chain kernel/locking/lockdep.c:3909 [inline]
 __lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235
 lock_acquire kernel/locking/lockdep.c:5866 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823
 __mutex_lock_common kernel/locking/mutex.c:601 [inline]
 __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
 smc_vlan_by_tcpsk+0x251/0x620 net/smc/smc_core.c:1908
 __smc_connect+0x44b/0x4880 net/smc/af_smc.c:1520
 smc_connect_work+0x54c/0xae0 net/smc/af_smc.c:1613
 process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3319 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
 kthread+0x3c2/0x780 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>