======================================================
WARNING: possible circular locking dependency detected
6.12.0-rc3-next-20241016-syzkaller #0 Not tainted
------------------------------------------------------
syz.2.724/7757 is trying to acquire lock:
ffffffff8fcdca48 (rtnl_mutex){+.+.}-{3:3}, at: smc_vlan_by_tcpsk+0x399/0x4e0 net/smc/smc_core.c:1898

but task is already holding lock:
ffff888071930258 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1617 [inline]
ffff888071930258 (sk_lock-AF_INET6){+.+.}-{0:0}, at: smc_connect+0xb7/0xde0 net/smc/af_smc.c:1642

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (sk_lock-AF_INET6){+.+.}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       lock_sock_nested+0x48/0x100 net/core/sock.c:3619
       do_ipv6_setsockopt+0xbf7/0x3640 net/ipv6/ipv6_sockglue.c:567
       ipv6_setsockopt+0x5d/0x170 net/ipv6/ipv6_sockglue.c:993
       do_sock_setsockopt+0x3af/0x720 net/socket.c:2334
       __sys_setsockopt+0x1a2/0x250 net/socket.c:2357
       __do_sys_setsockopt net/socket.c:2366 [inline]
       __se_sys_setsockopt net/socket.c:2363 [inline]
       __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2363
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (rtnl_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
       __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5202
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       smc_vlan_by_tcpsk+0x399/0x4e0 net/smc/smc_core.c:1898
       __smc_connect+0x292/0x1850 net/smc/af_smc.c:1518
       smc_connect+0x868/0xde0 net/smc/af_smc.c:1694
       __sys_connect_file net/socket.c:2071 [inline]
       __sys_connect+0x2d1/0x300 net/socket.c:2088
       __do_sys_connect net/socket.c:2098 [inline]
       __se_sys_connect net/socket.c:2095 [inline]
       __x64_sys_connect+0x7a/0x90 net/socket.c:2095
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sk_lock-AF_INET6);
                               lock(rtnl_mutex);
                               lock(sk_lock-AF_INET6);
  lock(rtnl_mutex);

 *** DEADLOCK ***

1 lock held by syz.2.724/7757:
 #0: ffff888071930258 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1617 [inline]
 #0: ffff888071930258 (sk_lock-AF_INET6){+.+.}-{0:0}, at: smc_connect+0xb7/0xde0 net/smc/af_smc.c:1642

stack backtrace:
CPU: 0 UID: 0 PID: 7757 Comm: syz.2.724 Not tainted 6.12.0-rc3-next-20241016-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206
 check_prev_add kernel/locking/lockdep.c:3161 [inline]
 check_prevs_add kernel/locking/lockdep.c:3280 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
 __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5202
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
 smc_vlan_by_tcpsk+0x399/0x4e0 net/smc/smc_core.c:1898
 __smc_connect+0x292/0x1850 net/smc/af_smc.c:1518
 smc_connect+0x868/0xde0 net/smc/af_smc.c:1694
 __sys_connect_file net/socket.c:2071 [inline]
 __sys_connect+0x2d1/0x300 net/socket.c:2088
 __do_sys_connect net/socket.c:2098 [inline]
 __se_sys_connect net/socket.c:2095 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:2095
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3296b7dff9
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:00007f32978b0038 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007f3296d35f80 RCX: 00007f3296b7dff9
RDX: 000000000000001c RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00007f3296bf0296 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f3296d35f80 R15: 00007fff9fb0a878
 </TASK>