Hello, syzbot hit the following crash on net-next commit 617aebe6a97efa539cc4b8a52adccd89596e6be0 (Sun Feb 4 00:25:42 2018 +0000) Merge tag 'usercopy-v4.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux So far this crash happened 2510 times on net-next, upstream. C reproducer is attached. syzkaller reproducer is attached. Raw console output is attached. compiler: gcc (GCC) 7.1.1 20170620 .config is attached. IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+63682ce11532e0da2b9d@syzkaller.appspotmail.com It will help syzbot understand when the bug is fixed. See footer for details. If you forward the report, please keep this part and the footer. ====================================================== WARNING: possible circular locking dependency detected 4.15.0+ #221 Not tainted ------------------------------------------------------ syzkaller414214/4173 is trying to acquire lock: (rtnl_mutex){+.+.}, at: [<000000003cc93f9b>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74 but task is already holding lock: (&xt[i].mutex){+.+.}, at: [<0000000059cfac75>] xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1041 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&xt[i].mutex){+.+.}: __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 xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1041 xt_request_find_table_lock+0x28/0xc0 net/netfilter/x_tables.c:1088 get_info+0x154/0x690 net/ipv6/netfilter/ip6_tables.c:989 do_ipt_get_ctl+0x159/0xac0 net/ipv4/netfilter/ip_tables.c:1699 nf_sockopt net/netfilter/nf_sockopt.c:104 [inline] nf_getsockopt+0x6a/0xc0 net/netfilter/nf_sockopt.c:122 ip_getsockopt+0x15c/0x220 net/ipv4/ip_sockglue.c:1571 tcp_getsockopt+0x82/0xd0 net/ipv4/tcp.c:3359 sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2934 SYSC_getsockopt net/socket.c:1880 [inline] SyS_getsockopt+0x178/0x340 net/socket.c:1862 entry_SYSCALL_64_fastpath+0x29/0xa0 -> #1 (sk_lock-AF_INET){+.+.}: lock_sock_nested+0xc2/0x110 net/core/sock.c:2777 lock_sock include/net/sock.h:1463 [inline] do_ip_setsockopt.isra.12+0x1d9/0x3210 net/ipv4/ip_sockglue.c:646 ip_setsockopt+0x3a/0xa0 net/ipv4/ip_sockglue.c:1252 udp_setsockopt+0x45/0x80 net/ipv4/udp.c:2401 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2975 SYSC_setsockopt net/socket.c:1849 [inline] SyS_setsockopt+0x189/0x360 net/socket.c:1828 entry_SYSCALL_64_fastpath+0x29/0xa0 -> #0 (rtnl_mutex){+.+.}: 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 unregister_netdevice_notifier+0x91/0x4e0 net/core/dev.c:1673 clusterip_config_entry_put net/ipv4/netfilter/ipt_CLUSTERIP.c:114 [inline] clusterip_tg_destroy+0x389/0x6e0 net/ipv4/netfilter/ipt_CLUSTERIP.c:518 cleanup_entry+0x218/0x350 net/ipv4/netfilter/ip_tables.c:654 __do_replace+0x79d/0xa50 net/ipv4/netfilter/ip_tables.c:1089 do_replace net/ipv4/netfilter/ip_tables.c:1145 [inline] do_ipt_set_ctl+0x40f/0x5f0 net/ipv4/netfilter/ip_tables.c:1675 nf_sockopt net/netfilter/nf_sockopt.c:106 [inline] nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:115 ip_setsockopt+0x97/0xa0 net/ipv4/ip_sockglue.c:1259 tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2905 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2975 SYSC_setsockopt net/socket.c:1849 [inline] SyS_setsockopt+0x189/0x360 net/socket.c:1828 entry_SYSCALL_64_fastpath+0x29/0xa0 other info that might help us debug this: Chain exists of: rtnl_mutex --> sk_lock-AF_INET --> &xt[i].mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&xt[i].mutex); lock(sk_lock-AF_INET); lock(&xt[i].mutex); lock(rtnl_mutex); *** DEADLOCK *** 1 lock held by syzkaller414214/4173: #0: (&xt[i].mutex){+.+.}, at: [<0000000059cfac75>] xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1041 stack backtrace: CPU: 1 PID: 4173 Comm: syzkaller414214 Not tainted 4.15.0+ #221 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+0x194/0x257 lib/dump_stack.c:53 print_circular_bug.isra.38+0x2cd/0x2dc kernel/locking/lockdep.c:1223 check_prev_add kernel/locking/lockdep.c:1863 [inline] check_prevs_add kernel/locking/lockdep.c:1976 [inline] validate_chain kernel/locking/lockdep.c:2417 [inline] __lock_acquire+0x30a8/0x3e00 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 unregister_netdevice_notifier+0x91/0x4e0 net/core/dev.c:1673 clusterip_config_entry_put net/ipv4/netfilter/ipt_CLUSTERIP.c:114 [inline] clusterip_tg_destroy+0x389/0x6e0 net/ipv4/netfilter/ipt_CLUSTERIP.c:518 cleanup_entry+0x218/0x350 net/ipv4/netfilter/ip_tables.c:654 __do_replace+0x79d/0xa50 net/ipv4/netfilter/ip_tables.c:1089 do_replace net/ipv4/netfilter/ip_tables.c:1145 [inline] do_ipt_set_ctl+0x40f/0x5f0 net/ipv4/netfilter/ip_tables.c:1675 nf_sockopt net/netfilter/nf_sockopt.c:106 [inline] nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:115 ip_setsockopt+0x97/0xa0 net/ipv4/ip_sockglue.c:1259 tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2905 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2975 SYSC_setsockopt net/socket.c:1849 [inline] SyS_setsockopt+0x189/0x360 net/socket.c:1828 entry_SYSCALL_64_fastpath+0x29/0xa0 RIP: 0033:0x4443da RSP: 002b:00007ffe9e2704d8 EFLAGS: 00000206 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 00000000006cc100 RCX: 00000000004443da RDX: 0000000000000040 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00000000006cc100 R08: 00000000000002d8 R09: 000000000106b880 R10: 00000000006cc528 R11: 0000000000000206 R12: 0000000000000003 R13: 00000000006cf0a8 R14: 00000000006cf050 R15: 00000000004a338e --- This bug is generated by a dumb bot. 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