[....] Starting enhanced syslogd: rsyslogd[ 13.958897] audit: type=1400 audit(1541982017.823:4): avc: denied { syslog } for pid=1920 comm="rsyslogd" capability=34 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:system_r:kernel_t:s0 tclass=capability2 permissive=1 [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Starting mcstransd: [....] Starting file context maintaining daemon: restorecond[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.84' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 47.746223] [ 47.747872] ====================================================== [ 47.754167] [ INFO: possible circular locking dependency detected ] [ 47.760549] 4.4.163+ #11 Not tainted [ 47.764236] ------------------------------------------------------- [ 47.770660] syz-executor066/2085 is trying to acquire lock: [ 47.776353] (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 [ 47.784274] [ 47.784274] but task is already holding lock: [ 47.790223] (sk_lock-AF_INET6){+.+.+.}, at: [] do_ipv6_setsockopt.isra.4+0x252/0x2d50 [ 47.800319] [ 47.800319] which lock already depends on the new lock. [ 47.800319] [ 47.808616] [ 47.808616] the existing dependency chain (in reverse order) is: [ 47.816211] -> #1 (sk_lock-AF_INET6){+.+.+.}: [ 47.821485] [] lock_acquire+0x15e/0x450 [ 47.827735] [] lock_sock_nested+0xc6/0x120 [ 47.834240] [] do_ipv6_setsockopt.isra.4+0x1d2/0x2d50 [ 47.841714] [] compat_ipv6_setsockopt+0xe9/0x1d0 [ 47.848740] [] compat_udpv6_setsockopt+0x4a/0x90 [ 47.856288] [] compat_sock_common_setsockopt+0xb4/0x150 [ 47.864105] [] compat_SyS_setsockopt+0x169/0x700 [ 47.871390] [] do_fast_syscall_32+0x31e/0xa80 [ 47.878161] [] sysenter_flags_fixed+0xd/0x1a [ 47.884837] -> #0 (rtnl_mutex){+.+.+.}: [ 47.889456] [] __lock_acquire+0x3e6c/0x5f10 [ 47.896055] [] lock_acquire+0x15e/0x450 [ 47.902299] [] mutex_lock_nested+0xbb/0x8d0 [ 47.908897] [] rtnl_lock+0x17/0x20 [ 47.914707] [] ipv6_sock_mc_close+0x10e/0x350 [ 47.921468] [] do_ipv6_setsockopt.isra.4+0xd07/0x2d50 [ 47.928931] [] compat_ipv6_setsockopt+0xe9/0x1d0 [ 47.935961] [] compat_udpv6_setsockopt+0x4a/0x90 [ 47.942995] [] compat_sock_common_setsockopt+0xb4/0x150 [ 47.950645] [] compat_SyS_setsockopt+0x169/0x700 [ 47.957684] [] do_fast_syscall_32+0x31e/0xa80 [ 47.964454] [] sysenter_flags_fixed+0xd/0x1a [ 47.971233] [ 47.971233] other info that might help us debug this: [ 47.971233] [ 47.979353] Possible unsafe locking scenario: [ 47.979353] [ 47.985385] CPU0 CPU1 [ 47.990034] ---- ---- [ 47.994678] lock(sk_lock-AF_INET6); [ 47.998747] lock(rtnl_mutex); [ 48.004763] lock(sk_lock-AF_INET6); [ 48.011302] lock(rtnl_mutex); [ 48.014797] [ 48.014797] *** DEADLOCK *** [ 48.014797] [ 48.020839] 1 lock held by syz-executor066/2085: [ 48.025570] #0: (sk_lock-AF_INET6){+.+.+.}, at: [] do_ipv6_setsockopt.isra.4+0x252/0x2d50 [ 48.036220] [ 48.036220] stack backtrace: [ 48.040698] CPU: 0 PID: 2085 Comm: syz-executor066 Not tainted 4.4.163+ #11 [ 48.047775] 0000000000000000 5e6dad46a1524676 ffff8801d3e77538 ffffffff81aa556d [ 48.055775] ffffffff83a85b10 ffffffff83ac48d0 ffffffff83a85b10 ffff8800b6efd028 [ 48.063769] ffff8800b6efc740 ffff8801d3e77580 ffffffff813a8827 0000000000000001 [ 48.071757] Call Trace: [ 48.074590] [] dump_stack+0xc1/0x124 [ 48.079939] [] print_circular_bug.cold.34+0x2f7/0x432 [ 48.086763] [] __lock_acquire+0x3e6c/0x5f10 [ 48.092721] [] ? trace_hardirqs_on+0x10/0x10 [ 48.098764] [] lock_acquire+0x15e/0x450 [ 48.104372] [] ? rtnl_lock+0x17/0x20 [ 48.109726] [] ? rtnl_lock+0x17/0x20 [ 48.115142] [] mutex_lock_nested+0xbb/0x8d0 [ 48.121099] [] ? rtnl_lock+0x17/0x20 [ 48.126441] [] ? debug_lockdep_rcu_enabled+0x77/0x90 [ 48.133171] [] ? debug_lockdep_rcu_enabled+0x77/0x90 [ 48.139912] [] ? mutex_trylock+0x3e0/0x3e0 [ 48.145828] [] ? mark_held_locks+0xc7/0x130 [ 48.151788] [] ? __local_bh_enable_ip+0x6a/0xe0 [ 48.158092] [] rtnl_lock+0x17/0x20 [ 48.163262] [] ipv6_sock_mc_close+0x10e/0x350 [ 48.169389] [] ? fl6_free_socklist+0xb7/0x240 [ 48.175576] [] do_ipv6_setsockopt.isra.4+0xd07/0x2d50 [ 48.182409] [] ? ip6_ra_control+0x430/0x430 [ 48.188366] [] ? trace_hardirqs_on+0x10/0x10 [ 48.194414] [] ? __lock_acquire+0xa85/0x5f10 [ 48.200462] [] ? __local_bh_enable_ip+0x6a/0xe0 [ 48.206759] [] ? debug_lockdep_rcu_enabled+0x77/0x90 [ 48.213497] [] ? avc_has_perm+0x15a/0x3a0 [ 48.219274] [] ? avc_has_perm+0x1cc/0x3a0 [ 48.225123] [] ? avc_has_perm+0x9e/0x3a0 [ 48.230825] [] ? avc_has_perm_noaudit+0x2f0/0x2f0 [ 48.237349] [] ? check_preemption_disabled+0x3b/0x200 [ 48.244185] [] ? sock_has_perm+0x1c1/0x3f0 [ 48.250068] [] ? sock_has_perm+0x2a1/0x3f0 [ 48.255933] [] ? sock_has_perm+0x9f/0x3f0 [ 48.261711] [] ? selinux_msg_queue_alloc_security+0x2e0/0x2e0 [ 48.269227] [] ? __fget+0x12f/0x3d0 [ 48.274483] [] compat_ipv6_setsockopt+0xe9/0x1d0 [ 48.280921] [] compat_udpv6_setsockopt+0x4a/0x90 [ 48.287324] [] compat_sock_common_setsockopt+0xb4/0x150 [ 48.294319] [] ? udpv6_setsockopt+0x90/0x90 [ 48.300269] [] compat_SyS_setsockopt+0x169/0x700 [ 48.306652] [] ? sock_common_setsockopt+0xe0/0xe0 [ 48.313120] [] ? scm_detach_fds_compat+0x3b0/0x3b0 [ 48.319676] [] ? __do_page_fault+0x2b6/0x7e0 [ 48.325709] [] ? do_fast_syscall_32+0xdb/0xa80 [ 48.331913] [] ? scm_detach_fds_compat+0x3b0/0x3b0 [ 48.338483] [] do_fast_syscall_32+0x31e/0xa80 [ 48.344615] [] sysenter_flags_