IPVS: stopping backup sync thread 4120 ... IPVS: stopping backup sync thread 4124 ... IPVS: stopping backup sync thread 4126 ... ============================================= [ INFO: possible recursive locking detected ] 4.4.128-gbd23e3a #20 Not tainted --------------------------------------------- syz-executor403/4093 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-executor403/4093: #0: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70 #1: (ipvs->sync_mutex){+.+.+.}, at: [] do_ip_vs_set_ctl+0x8e0/0xb70 net/netfilter/ipvs/ip_vs_ctl.c:2356 stack backtrace: CPU: 0 PID: 4093 Comm: syz-executor403 Not tainted 4.4.128-gbd23e3a #20 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 0000000000000000 4e287cbf125019bf ffff8800baef74f0 ffffffff81e0daad ffffffff8539cfa0 ffffffff8539cfa0 ffffffff8539cfa0 ffff8800afa6e900 00000002d873a0b6 ffff8800baef7698 ffffffff8140faf1 ffffffff85746f00 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.cold.58+0x154/0x58a kernel/locking/lockdep.c:3213 [] lock_acquire+0x15e/0x450 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+0x8c/0x230 net/ipv4/igmp.c:2590 [] inet_release+0x5b/0x1d0 net/ipv4/af_inet.c:421 [] sock_release+0x96/0x1c0 net/socket.c:586 [] start_sync_thread+0xa18/0x1ed0 net/netfilter/ipvs/ip_vs_sync.c:1923 [] do_ip_vs_set_ctl+0x8f2/0xb70 net/netfilter/ipvs/ip_vs_ctl.c:2357 [] nf_sockopt net/netfilter/nf_sockopt.c:105 [inline] [] nf_setsockopt+0x6d/0xc0 net/netfilter/nf_sockopt.c:114 [] ip_setsockopt+0x9a/0xb0 net/ipv4/ip_sockglue.c:1227 [] tcp_setsockopt+0x88/0xe0 net/ipv4/tcp.c:2641 [] sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:2659 [] SYSC_setsockopt net/socket.c:1767 [inline] [] SyS_setsockopt+0x166/0x260 net/socket.c:1746 [] entry_SYSCALL_64_fastpath+0x22/0x9e