======================================================
WARNING: possible circular locking dependency detected
6.11.0-syzkaller-11624-ge477dba5442c #0 Not tainted
------------------------------------------------------
syz.2.121/5772 is trying to acquire lock:
ffff88802771dea8 (&smc->clcsock_release_lock){+.+.}-{3:3}, at: smc_switch_to_fallback+0x2d/0xa00 net/smc/af_smc.c:902

but task is already holding lock:
ffff88802771d658 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1609 [inline]
ffff88802771d658 (sk_lock-AF_INET6){+.+.}-{0:0}, at: smc_sendmsg+0x47/0x520 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_sock_nested+0x3a/0xf0 net/core/sock.c:3611
       lock_sock include/net/sock.h:1609 [inline]
       sockopt_lock_sock net/core/sock.c:1125 [inline]
       sockopt_lock_sock+0x54/0x70 net/core/sock.c:1116
       do_ipv6_setsockopt+0x1f55/0x4800 net/ipv6/ipv6_sockglue.c:567
       ipv6_setsockopt+0xcb/0x170 net/ipv6/ipv6_sockglue.c:993
       udpv6_setsockopt+0x7d/0xd0 net/ipv6/udp.c:1702
       do_sock_setsockopt+0x222/0x480 net/socket.c:2329
       __sys_setsockopt+0x1a4/0x270 net/socket.c:2352
       __do_sys_setsockopt net/socket.c:2361 [inline]
       __se_sys_setsockopt net/socket.c:2358 [inline]
       __x64_sys_setsockopt+0xbd/0x160 net/socket.c:2358
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (rtnl_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
       do_ipv6_setsockopt+0x1f4d/0x4800 net/ipv6/ipv6_sockglue.c:566
       ipv6_setsockopt+0xcb/0x170 net/ipv6/ipv6_sockglue.c:993
       tcp_setsockopt+0xa4/0x100 net/ipv4/tcp.c:4029
       smc_setsockopt+0x1b4/0xc00 net/smc/af_smc.c:3064
       do_sock_setsockopt+0x222/0x480 net/socket.c:2329
       __sys_setsockopt+0x1a4/0x270 net/socket.c:2352
       __do_sys_setsockopt net/socket.c:2361 [inline]
       __se_sys_setsockopt net/socket.c:2358 [inline]
       __x64_sys_setsockopt+0xbd/0x160 net/socket.c:2358
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 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:3158 [inline]
       check_prevs_add kernel/locking/lockdep.c:3277 [inline]
       validate_chain kernel/locking/lockdep.c:3901 [inline]
       __lock_acquire+0x250b/0x3ce0 kernel/locking/lockdep.c:5199
       lock_acquire kernel/locking/lockdep.c:5822 [inline]
       lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5787
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
       smc_switch_to_fallback+0x2d/0xa00 net/smc/af_smc.c:902
       smc_sendmsg+0x13d/0x520 net/smc/af_smc.c:2771
       sock_sendmsg_nosec net/socket.c:729 [inline]
       __sock_sendmsg net/socket.c:744 [inline]
       ____sys_sendmsg+0x9ae/0xb40 net/socket.c:2602
       ___sys_sendmsg+0x135/0x1e0 net/socket.c:2656
       __sys_sendmsg+0x117/0x1f0 net/socket.c:2685
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 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.2.121/5772:
 #0: ffff88802771d658 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1609 [inline]
 #0: ffff88802771d658 (sk_lock-AF_INET6){+.+.}-{0:0}, at: smc_sendmsg+0x47/0x520 net/smc/af_smc.c:2765

stack backtrace:
CPU: 0 UID: 0 PID: 5772 Comm: syz.2.121 Not tainted 6.11.0-syzkaller-11624-ge477dba5442c #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+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x419/0x5d0 kernel/locking/lockdep.c:2074
 check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2203
 check_prev_add kernel/locking/lockdep.c:3158 [inline]
 check_prevs_add kernel/locking/lockdep.c:3277 [inline]
 validate_chain kernel/locking/lockdep.c:3901 [inline]
 __lock_acquire+0x250b/0x3ce0 kernel/locking/lockdep.c:5199
 lock_acquire kernel/locking/lockdep.c:5822 [inline]
 lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5787
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
 smc_switch_to_fallback+0x2d/0xa00 net/smc/af_smc.c:902
 smc_sendmsg+0x13d/0x520 net/smc/af_smc.c:2771
 sock_sendmsg_nosec net/socket.c:729 [inline]
 __sock_sendmsg net/socket.c:744 [inline]
 ____sys_sendmsg+0x9ae/0xb40 net/socket.c:2602
 ___sys_sendmsg+0x135/0x1e0 net/socket.c:2656
 __sys_sendmsg+0x117/0x1f0 net/socket.c:2685
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f443117df39
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:00007f4431ea3038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f4431335f80 RCX: 00007f443117df39
RDX: 0000000020008811 RSI: 0000000020000140 RDI: 0000000000000004
RBP: 00007f44311f0216 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f4431335f80 R15: 00007ffd116a5688
 </TASK>