syzbot

IPVS: stopping backup sync thread 5953 ...
======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc2-syzkaller-00048-gc62f4b82d571 #0 Not tainted
------------------------------------------------------
syz.2.1214/9924 is trying to acquire lock:
ffffffff900fd588 (rtnl_mutex){+.+.}-{4:4}, at: ip_mc_drop_socket+0x81/0x280 net/ipv4/igmp.c:2790

but task is already holding lock:
ffff8880354c21a8 (&smc->clcsock_release_lock){+.+.}-{4:4}, at: smc_setsockopt+0x1b2/0xd50 net/smc/af_smc.c:3073

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&smc->clcsock_release_lock){+.+.}-{4:4}:
       lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x1a5/0x10c0 kernel/locking/mutex.c:746
       smc_switch_to_fallback+0x35/0xda0 net/smc/af_smc.c:903
       smc_sendmsg+0x11f/0x530 net/smc/af_smc.c:2781
       sock_sendmsg_nosec net/socket.c:712 [inline]
       __sock_sendmsg+0x221/0x270 net/socket.c:727
       __sys_sendto+0x365/0x4c0 net/socket.c:2180
       __do_sys_sendto net/socket.c:2187 [inline]
       __se_sys_sendto net/socket.c:2183 [inline]
       __x64_sys_sendto+0xde/0x100 net/socket.c:2183
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (sk_lock-AF_INET){+.+.}-{0:0}:
       lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
       lock_sock_nested+0x48/0x100 net/core/sock.c:3702
       do_ip_setsockopt+0x17e9/0x39c0 net/ipv4/ip_sockglue.c:1078
       ip_setsockopt+0x63/0x100 net/ipv4/ip_sockglue.c:1417
       do_sock_setsockopt+0x3b1/0x710 net/socket.c:2296
       __sys_setsockopt net/socket.c:2321 [inline]
       __do_sys_setsockopt net/socket.c:2327 [inline]
       __se_sys_setsockopt net/socket.c:2324 [inline]
       __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2324
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf3/0x230 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+0xa69/0x24e0 kernel/locking/lockdep.c:3909
       __lock_acquire+0xad5/0xd80 kernel/locking/lockdep.c:5235
       lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x1a5/0x10c0 kernel/locking/mutex.c:746
       ip_mc_drop_socket+0x81/0x280 net/ipv4/igmp.c:2790
       inet_release+0x96/0x200 net/ipv4/af_inet.c:422
       __sock_release net/socket.c:647 [inline]
       sock_release+0x82/0x150 net/socket.c:675
       stop_sync_thread+0x4ec/0x5e0 net/netfilter/ipvs/ip_vs_sync.c:2004
       do_ip_vs_set_ctl+0x4c1/0xe50 net/netfilter/ipvs/ip_vs_ctl.c:2734
       nf_setsockopt+0x295/0x2c0 net/netfilter/nf_sockopt.c:101
       smc_setsockopt+0x25c/0xd50 net/smc/af_smc.c:3081
       do_sock_setsockopt+0x3b1/0x710 net/socket.c:2296
       __sys_setsockopt net/socket.c:2321 [inline]
       __do_sys_setsockopt net/socket.c:2327 [inline]
       __se_sys_setsockopt net/socket.c:2324 [inline]
       __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2324
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

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

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

1 lock held by syz.2.1214/9924:
 #0: ffff8880354c21a8 (&smc->clcsock_release_lock){+.+.}-{4:4}, at: smc_setsockopt+0x1b2/0xd50 net/smc/af_smc.c:3073

stack backtrace:
CPU: 1 UID: 0 PID: 9924 Comm: syz.2.1214 Not tainted 6.15.0-rc2-syzkaller-00048-gc62f4b82d571 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2079
 check_noncircular+0x142/0x160 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+0xa69/0x24e0 kernel/locking/lockdep.c:3909
 __lock_acquire+0xad5/0xd80 kernel/locking/lockdep.c:5235
 lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
 __mutex_lock_common kernel/locking/mutex.c:601 [inline]
 __mutex_lock+0x1a5/0x10c0 kernel/locking/mutex.c:746
 ip_mc_drop_socket+0x81/0x280 net/ipv4/igmp.c:2790
 inet_release+0x96/0x200 net/ipv4/af_inet.c:422
 __sock_release net/socket.c:647 [inline]
 sock_release+0x82/0x150 net/socket.c:675
 stop_sync_thread+0x4ec/0x5e0 net/netfilter/ipvs/ip_vs_sync.c:2004
 do_ip_vs_set_ctl+0x4c1/0xe50 net/netfilter/ipvs/ip_vs_ctl.c:2734
 nf_setsockopt+0x295/0x2c0 net/netfilter/nf_sockopt.c:101
 smc_setsockopt+0x25c/0xd50 net/smc/af_smc.c:3081
 do_sock_setsockopt+0x3b1/0x710 net/socket.c:2296
 __sys_setsockopt net/socket.c:2321 [inline]
 __do_sys_setsockopt net/socket.c:2327 [inline]
 __se_sys_setsockopt net/socket.c:2324 [inline]
 __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2324
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fcc21f8e169
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:00007fcc22d21038 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007fcc221b6080 RCX: 00007fcc21f8e169
RDX: 000000000000048c RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007fcc22010a68 R08: 0000000000000018 R09: 0000000000000000
R10: 0000200000000080 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fcc221b6080 R15: 00007fcc222dfa28
 </TASK>