IPVS: sync thread started: state = BACKUP, mcast_ifn = tunl0, syncid = 0, id = 0 IPVS: stopping backup sync thread 4524 ... IPVS: sync thread started: state = BACKUP, mcast_ifn = tunl0, syncid = 0, id = 0 ============================================ WARNING: possible recursive locking detected 4.16.0-rc7+ #278 Not tainted -------------------------------------------- syz-executor2/4514 is trying to acquire lock: (rtnl_mutex){+.+.}, at: [<0000000027e9f135>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74 but task is already holding lock: (rtnl_mutex){+.+.}, at: [<0000000027e9f135>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(rtnl_mutex); lock(rtnl_mutex); *** DEADLOCK *** May be due to missing lock nesting notation 2 locks held by syz-executor2/4514: #0: (rtnl_mutex){+.+.}, at: [<0000000027e9f135>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74 #1: (ipvs->sync_mutex){+.+.}, at: [<0000000098b55d93>] do_ip_vs_set_ctl+0x10f8/0x1cc0 net/netfilter/ipvs/ip_vs_ctl.c:2388 stack backtrace: CPU: 0 PID: 4514 Comm: syz-executor2 Not tainted 4.16.0-rc7+ #278 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x24d lib/dump_stack.c:53 print_deadlock_bug kernel/locking/lockdep.c:1761 [inline] check_deadlock kernel/locking/lockdep.c:1805 [inline] validate_chain kernel/locking/lockdep.c:2401 [inline] __lock_acquire+0xe8f/0x3e00 kernel/locking/lockdep.c:3431 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74 ip_mc_drop_socket+0x88/0x230 net/ipv4/igmp.c:2643 inet_release+0x4e/0x1c0 net/ipv4/af_inet.c:413 sock_release+0x8d/0x1e0 net/socket.c:595 start_sync_thread+0x2213/0x2b70 net/netfilter/ipvs/ip_vs_sync.c:1924 do_ip_vs_set_ctl+0x1139/0x1cc0 net/netfilter/ipvs/ip_vs_ctl.c:2389 compat_nf_sockopt net/netfilter/nf_sockopt.c:146 [inline] compat_nf_setsockopt+0xfa/0x130 net/netfilter/nf_sockopt.c:156 compat_ip_setsockopt+0x8b/0xd0 net/ipv4/ip_sockglue.c:1287 inet_csk_compat_setsockopt+0x95/0x120 net/ipv4/inet_connection_sock.c:1041 compat_tcp_setsockopt+0x3d/0x70 net/ipv4/tcp.c:2916 compat_sock_common_setsockopt+0xb2/0x140 net/core/sock.c:2986 C_SYSC_setsockopt net/compat.c:403 [inline] compat_SyS_setsockopt+0x17c/0x410 net/compat.c:386 do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline] do_fast_syscall_32+0x3ec/0xf9f arch/x86/entry/common.c:392 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 RIP: 0023:0xf7f08c99 RSP: 002b:00000000f7f0409c EFLAGS: 00000286 ORIG_RAX: 000000000000016e RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000000 RDX: 000000000000048b RSI: 0000000020000040 RDI: 0000000000000018 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 IPVS: stopping backup sync thread 4529 ...