random: sshd: uninitialized urandom read (32 bytes read, 124 bits of entropy available) random: sshd: uninitialized urandom read (32 bytes read, 128 bits of entropy available) TCP: request_sock_TCP: Possible SYN flooding on port 20002. Sending cookies. Check SNMP counters. ====================================================== [ INFO: possible circular locking dependency detected ] 4.4.118-g239a415 #25 Not tainted ------------------------------------------------------- syzkaller915933/3675 is trying to acquire lock: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70 but task is already holding lock: (sk_lock-AF_INET6){+.+.+.}, at: [] lock_sock include/net/sock.h:1493 [inline] (sk_lock-AF_INET6){+.+.+.}, at: [] do_ipv6_setsockopt.isra.8+0x1e2/0x3030 net/ipv6/ipv6_sockglue.c:166 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: [] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592 [] lock_sock_nested+0xc6/0x120 net/core/sock.c:2459 [] lock_sock include/net/sock.h:1493 [inline] [] do_ipv6_setsockopt.isra.8+0x331/0x3030 net/ipv6/ipv6_sockglue.c:166 [] ipv6_setsockopt+0xd7/0x130 net/ipv6/ipv6_sockglue.c:904 [] tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2641 [] sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2659 [] SYSC_setsockopt net/socket.c:1767 [inline] [] SyS_setsockopt+0x160/0x250 net/socket.c:1746 [] entry_SYSCALL_64_fastpath+0x1c/0x98 [] check_prev_add kernel/locking/lockdep.c:1853 [inline] [] check_prevs_add kernel/locking/lockdep.c:1958 [inline] [] validate_chain kernel/locking/lockdep.c:2144 [inline] [] __lock_acquire+0x371f/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 [] ipv6_sock_mc_close+0x10e/0x350 net/ipv6/mcast.c:288 [] do_ipv6_setsockopt.isra.8+0x13c1/0x3030 net/ipv6/ipv6_sockglue.c:202 [] ipv6_setsockopt+0xd7/0x130 net/ipv6/ipv6_sockglue.c:904 [] tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2641 [] sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2659 [] SYSC_setsockopt net/socket.c:1767 [inline] [] SyS_setsockopt+0x160/0x250 net/socket.c:1746 [] entry_SYSCALL_64_fastpath+0x1c/0x98 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sk_lock-AF_INET6); lock(rtnl_mutex); lock(sk_lock-AF_INET6); lock(rtnl_mutex); *** DEADLOCK *** 1 lock held by syzkaller915933/3675: #0: (sk_lock-AF_INET6){+.+.+.}, at: [] lock_sock include/net/sock.h:1493 [inline] #0: (sk_lock-AF_INET6){+.+.+.}, at: [] do_ipv6_setsockopt.isra.8+0x1e2/0x3030 net/ipv6/ipv6_sockglue.c:166 stack backtrace: CPU: 0 PID: 3675 Comm: syzkaller915933 Not tainted 4.4.118-g239a415 #25 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 0000000000000000 d6efcd04ca2e32c1 ffff8800b5ec75a8 ffffffff81d0402d ffffffff8516edb0 ffffffff8516edb0 ffffffff851b85e0 ffff8800afa120f8 ffff8800afa11800 ffff8800b5ec75f0 ffffffff81233ba1 ffff8800afa120f8 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x124 lib/dump_stack.c:51 [] print_circular_bug+0x271/0x310 kernel/locking/lockdep.c:1226 [] check_prev_add kernel/locking/lockdep.c:1853 [inline] [] check_prevs_add kernel/locking/lockdep.c:1958 [inline] [] validate_chain kernel/locking/lockdep.c:2144 [inline] [] __lock_acquire+0x371f/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 [] ipv6_sock_mc_close+0x10e/0x350 net/ipv6/mcast.c:288 [] do_ipv6_setsockopt.isra.8+0x13c1/0x3030 net/ipv6/ipv6_sockglue.c:202 [] ipv6_setsockopt+0xd7/0x130 net/ipv6/ipv6_sockglue.c:904 [] tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2641 [] sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2659 [] SYSC_setsockopt net/socket.c:1767 [inline] [] SyS_setsockopt+0x160/0x250 net/socket.c:1746 [] ? move_addr_to_ke