IPVS: stopping backup sync thread 4219 ... IPVS: sync thread started: state = BACKUP, mcast_ifn = tunl0, syncid = 0, id = 0 IPVS: stopping backup sync thread 4221 ... ============================================= [ INFO: possible recursive locking detected ] 4.9.90-gdd1e37e #66 Not tainted --------------------------------------------- syz-executor0/4223 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-executor0/4223: #0: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70 #1: (ipvs->sync_mutex){+.+.+.}, at: [] do_ip_vs_set_ctl+0x8e7/0xc00 net/netfilter/ipvs/ip_vs_ctl.c:2397 stack backtrace: CPU: 1 PID: 4223 Comm: syz-executor0 Not tainted 4.9.90-gdd1e37e #66 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801b1777460 ffffffff81d94ee9 ffffffff8536fd80 ffffffff8536fd80 dffffc0000000000 7e06f8cbd7b30dc5 0000000000000000 ffff8801b1777630 ffffffff8123b925 ffffffff84c6bca0 ffffffff84fc35b0 ffffffff84c6bca4 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] print_deadlock_bug kernel/locking/lockdep.c:1727 [inline] [] check_deadlock kernel/locking/lockdep.c:1771 [inline] [] validate_chain kernel/locking/lockdep.c:2249 [inline] [] __lock_acquire+0xe35/0x3640 kernel/locking/lockdep.c:3345 [] lock_acquire+0x12e/0x410 kernel/locking/lockdep.c:3756 [] __mutex_lock_common kernel/locking/mutex.c:521 [inline] [] mutex_lock_nested+0xbb/0x870 kernel/locking/mutex.c:621 [] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70 [] ip_mc_drop_socket+0x88/0x230 net/ipv4/igmp.c:2635 [] inet_release+0x5b/0x1d0 net/ipv4/af_inet.c:420 [] sock_release+0x8d/0x1e0 net/socket.c:599 [] start_sync_thread+0x191b/0x1ef0 net/netfilter/ipvs/ip_vs_sync.c:1926 [] do_ip_vs_set_ctl+0x8fb/0xc00 net/netfilter/ipvs/ip_vs_ctl.c:2398 [] nf_sockopt net/netfilter/nf_sockopt.c:105 [inline] [] nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:114 [] ip_setsockopt+0x97/0xa0 net/ipv4/ip_sockglue.c:1247 [] tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2755 [] sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2706 [] SYSC_setsockopt net/socket.c:1772 [inline] [] SyS_setsockopt+0x160/0x250 net/socket.c:1751 [] do_syscall_64+0x1a4/0x490 arch/x86/entry/common.c:282 [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb