======================================================
WARNING: possible circular locking dependency detected
6.12.0-rc7-syzkaller-00135-g8ffade77b633 #0 Not tainted
------------------------------------------------------
syz.2.1836/12784 is trying to acquire lock:
ffff888024290aa8 (&smc->clcsock_release_lock){+.+.}-{3:3}, at: smc_switch_to_fallback+0x35/0xdb0 net/smc/af_smc.c:902

but task is already holding lock:
ffff888024290258 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1611 [inline]
ffff888024290258 (sk_lock-AF_INET6){+.+.}-{0:0}, at: smc_sendmsg+0x55/0x530 net/smc/af_smc.c:2765

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (sk_lock-AF_INET6){+.+.}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       lock_sock_nested+0x48/0x100 net/core/sock.c:3617
       do_ipv6_setsockopt+0xbf3/0x3630 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

-> #1 (rtnl_mutex){+.+.}-{3:3}:
       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
       do_ip_setsockopt+0x127d/0x3cd0 net/ipv4/ip_sockglue.c:1077
       ip_setsockopt+0x63/0x100 net/ipv4/ip_sockglue.c:1417
       smc_setsockopt+0x275/0xe50 net/smc/af_smc.c:3064
       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 (&smc->clcsock_release_lock){+.+.}-{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_switch_to_fallback+0x35/0xdb0 net/smc/af_smc.c:902
       smc_sendmsg+0x11f/0x530 net/smc/af_smc.c:2771
       sock_sendmsg_nosec net/socket.c:729 [inline]
       __sock_sendmsg+0x221/0x270 net/socket.c:744
       ____sys_sendmsg+0x52a/0x7e0 net/socket.c:2607
       ___sys_sendmsg net/socket.c:2661 [inline]
       __sys_sendmsg+0x292/0x380 net/socket.c:2690
       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:

Chain exists of:
  &smc->clcsock_release_lock --> rtnl_mutex --> sk_lock-AF_INET6

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sk_lock-AF_INET6);
                               lock(rtnl_mutex);
                               lock(sk_lock-AF_INET6);
  lock(&smc->clcsock_release_lock);

 *** DEADLOCK ***

1 lock held by syz.2.1836/12784:
 #0: ffff888024290258 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1611 [inline]
 #0: ffff888024290258 (sk_lock-AF_INET6){+.+.}-{0:0}, at: smc_sendmsg+0x55/0x530 net/smc/af_smc.c:2765

stack backtrace:
CPU: 0 UID: 0 PID: 12784 Comm: syz.2.1836 Not tainted 6.12.0-rc7-syzkaller-00135-g8ffade77b633 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
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_switch_to_fallback+0x35/0xdb0 net/smc/af_smc.c:902
 smc_sendmsg+0x11f/0x530 net/smc/af_smc.c:2771
 sock_sendmsg_nosec net/socket.c:729 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:744
 ____sys_sendmsg+0x52a/0x7e0 net/socket.c:2607
 ___sys_sendmsg net/socket.c:2661 [inline]
 __sys_sendmsg+0x292/0x380 net/socket.c:2690
 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: 0033:0x7fb65a17e759
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:00007fb65afab038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fb65a336058 RCX: 00007fb65a17e759
RDX: 0000000020000e11 RSI: 0000000020000240 RDI: 0000000000000003
RBP: 00007fb65a1f175e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fb65a336058 R15: 00007ffd411fa268
 </TASK>