============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.1.17/4873 is trying to acquire lock:
ffff88810cf74858 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1693 [inline]
ffff88810cf74858 (sk_lock-AF_INET6){+.+.}-{0:0}, at: ipv6_sock_mc_close+0x2b/0x50 net/ipv6/mcast.c:348

but task is already holding lock:
ffff88810cf73f98 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1693 [inline]
ffff88810cf73f98 (sk_lock-AF_INET6){+.+.}-{0:0}, at: sctp_getsockopt+0x62/0x780 net/sctp/socket.c:8129

other info that might help us debug this:
 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

 May be due to missing lock nesting notation

1 lock held by syz.1.17/4873:
 #0: ffff88810cf73f98 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1693 [inline]
 #0: ffff88810cf73f98 (sk_lock-AF_INET6){+.+.}-{0:0}, at: sctp_getsockopt+0x62/0x780 net/sctp/socket.c:8129

stack backtrace:
CPU: 1 UID: 0 PID: 4873 Comm: syz.1.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0xad/0x110 lib/dump_stack.c:120
 print_deadlock_bug+0x210/0x220 kernel/locking/lockdep.c:3041
 check_deadlock kernel/locking/lockdep.c:3093 [inline]
 validate_chain kernel/locking/lockdep.c:3895 [inline]
 __lock_acquire+0x10a1/0x2100 kernel/locking/lockdep.c:5237
 lock_acquire+0xe9/0x270 kernel/locking/lockdep.c:5868
 lock_sock_nested+0x2e/0x70 net/core/sock.c:3762
 lock_sock include/net/sock.h:1693 [inline]
 ipv6_sock_mc_close+0x2b/0x50 net/ipv6/mcast.c:348
 inet6_release+0x1b/0x40 net/ipv6/af_inet6.c:482
 __sock_release net/socket.c:662 [inline]
 sock_release+0x24/0x90 net/socket.c:690
 sctp_getsockopt_peeloff_common+0x200/0x260 net/sctp/socket.c:5730
 sctp_getsockopt_peeloff_flags+0x7a/0x110 net/sctp/socket.c:5799
 sctp_getsockopt+0x257/0x780 net/sctp/socket.c:8149
 do_sock_getsockopt+0xd8/0x100 net/socket.c:2421
 __sys_getsockopt net/socket.c:2450 [inline]
 __do_sys_getsockopt net/socket.c:2457 [inline]
 __se_sys_getsockopt net/socket.c:2454 [inline]
 __x64_sys_getsockopt+0x95/0xe0 net/socket.c:2454
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xa6/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7feab958f749
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:00007feaba41e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 00007feab97e5fa0 RCX: 00007feab958f749
RDX: 000000000000007a RSI: 0000000000000084 RDI: 0000000000000003
RBP: 00007feab9613f91 R08: 0000200000000040 R09: 0000000000000000
R10: 0000200000000340 R11: 0000000000000246 R12: 0000000000000000
R13: 00007feab97e6038 R14: 00007feab97e5fa0 R15: 00007ffec3130a18
 </TASK>