IPVS: stopping backup sync thread 3943 ... IPVS: sync thread started: state = BACKUP, mcast_ifn = lo, syncid = 0, id = 0 IPVS: stopping backup sync thread 3948 ... ============================================= [ INFO: possible recursive locking detected ] 4.4.125-g38f41ec #21 Not tainted --------------------------------------------- syz-executor0/3947 is trying to acquire lock: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70 but task is already holding lock: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70 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-executor0/3947: #0: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70 #1: (ipvs->sync_mutex){+.+.+.}, at: [] do_ip_vs_set_ctl+0x8d3/0xba0 net/netfilter/ipvs/ip_vs_ctl.c:2356 stack backtrace: CPU: 1 PID: 3947 Comm: syz-executor0 Not tainted 4.4.125-g38f41ec #21 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 0000000000000000 77f201cc7a0844e0 ffff8800ac55f440 ffffffff81d067bd ffffffff85170f60 ffffffff85170f60 ffff8800ac8a6000 dffffc0000000000 ffff8800ac8a68e0 ffff8800ac55f5f0 ffffffff81238c40 ffffffff84a258a8 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x124 lib/dump_stack.c:51 [] print_deadlock_bug kernel/locking/lockdep.c:1752 [inline] [] check_deadlock kernel/locking/lockdep.c:1796 [inline] [] validate_chain kernel/locking/lockdep.c:2128 [inline] [] __lock_acquire+0x1350/0x4b50 kernel/locking/lockdep.c:3213 [] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592 [] __mutex_lock_common kernel/locking/mutex.c:521 [inline] [] mutex_lock_nested+0xbb/0x850 kernel/locking/mutex.c:621 [] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70 [] ip_mc_drop_socket+0x88/0x230 net/ipv4/igmp.c:2590 [] inet_release+0x5b/0x1d0 net/ipv4/af_inet.c:421 [] sock_release+0x8d/0x1e0 net/socket.c:586 [] start_sync_thread+0x196a/0x1f50 net/netfilter/ipvs/ip_vs_sync.c:1923 [] do_ip_vs_set_ctl+0x8e5/0xba0 net/netfilter/ipvs/ip_vs_ctl.c:2357 [] compat_nf_sockopt net/netfilter/nf_sockopt.c:145 [inline] [] compat_nf_setsockopt+0xfa/0x130 net/netfilter/nf_sockopt.c:155 [] compat_ip_setsockopt+0x8b/0xd0 net/ipv4/ip_sockglue.c:1251 [] compat_udp_setsockopt+0x45/0x80 net/ipv4/udp.c:2169 [] compat_ipv6_setsockopt+0xb3/0x1c0 net/ipv6/ipv6_sockglue.c:923 [] compat_udpv6_setsockopt+0x45/0x80 net/ipv6/udp.c:1446 [] compat_sock_common_setsockopt+0xb2/0x140 net/core/sock.c:2670 [] C_SYSC_setsockopt net/compat.c:384 [inline] [] compat_SyS_setsockopt+0x149/0x290 net/compat.c:367 [] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline] [] do_fast_syscall_32+0x321/0x8a0 arch/x86/entry/common.c:459 [] sysenter_flags_fixed+0xd/0x17