[....] Starting enhanced syslogd: rsyslogd[ 17.229812] audit: type=1400 audit(1554660731.047:4): avc: denied { syslog } for pid=1923 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 '10.128.0.37' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 70.518172] [ 70.519834] ====================================================== [ 70.526133] [ INFO: possible circular locking dependency detected ] [ 70.532635] 4.4.174+ #17 Not tainted [ 70.536329] ------------------------------------------------------- [ 70.542743] syz-executor126/2099 is trying to acquire lock: [ 70.548431] (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 [ 70.556402] [ 70.556402] but task is already holding lock: [ 70.562369] (sk_lock-AF_INET6){+.+.+.}, at: [] do_ipv6_setsockopt.isra.0+0x28a/0x30c0 [ 70.572491] [ 70.572491] which lock already depends on the new lock. [ 70.572491] [ 70.580789] [ 70.580789] the existing dependency chain (in reverse order) is: [ 70.588398] -> #1 (sk_lock-AF_INET6){+.+.+.}: [ 70.602269] [] lock_acquire+0x15e/0x450 [ 70.608544] [] lock_sock_nested+0xc6/0x120 [ 70.615073] [] do_ipv6_setsockopt.isra.0+0x2eba/0x30c0 [ 70.622630] [] ipv6_setsockopt+0xda/0x140 [ 70.629062] [] compat_mc_setsockopt+0x4f7/0x690 [ 70.636026] [] compat_ipv6_setsockopt+0x124/0x1d0 [ 70.643145] [] inet_csk_compat_setsockopt+0x99/0x120 [ 70.650566] [] compat_tcp_setsockopt+0x40/0x70 [ 70.657455] [] compat_sock_common_setsockopt+0xb4/0x150 [ 70.665129] [] compat_SyS_setsockopt+0x15c/0x720 [ 70.672192] [] do_fast_syscall_32+0x32d/0xa90 [ 70.679022] [] sysenter_flags_fixed+0xd/0x1a [ 70.692539] -> #0 (rtnl_mutex){+.+.+.}: [ 70.697182] [] __lock_acquire+0x37d6/0x4f50 [ 70.703872] [] lock_acquire+0x15e/0x450 [ 70.710142] [] mutex_lock_nested+0xc1/0xb80 [ 70.716771] [] rtnl_lock+0x17/0x20 [ 70.722617] [] ipv6_sock_mc_close+0x10e/0x350 [ 70.729474] [] do_ipv6_setsockopt.isra.0+0x1bd1/0x30c0 [ 70.737059] [] compat_ipv6_setsockopt+0xe7/0x1d0 [ 70.744107] [] inet_csk_compat_setsockopt+0x99/0x120 [ 70.751671] [] compat_tcp_setsockopt+0x40/0x70 [ 70.759852] [] compat_sock_common_setsockopt+0xb4/0x150 [ 70.767526] [] compat_SyS_setsockopt+0x15c/0x720 [ 70.774565] [] do_fast_syscall_32+0x32d/0xa90 [ 70.781596] [] sysenter_flags_fixed+0xd/0x1a [ 70.788298] [ 70.788298] other info that might help us debug this: [ 70.788298] [ 70.796422] Possible unsafe locking scenario: [ 70.796422] [ 70.802500] CPU0 CPU1 [ 70.807147] ---- ---- [ 70.811799] lock(sk_lock-AF_INET6); [ 70.815852] lock(rtnl_mutex); [ 70.821884] lock(sk_lock-AF_INET6); [ 70.828434] lock(rtnl_mutex); [ 70.831942] [ 70.831942] *** DEADLOCK *** [ 70.831942] [ 70.837984] 1 lock held by syz-executor126/2099: [ 70.842713] #0: (sk_lock-AF_INET6){+.+.+.}, at: [] do_ipv6_setsockopt.isra.0+0x28a/0x30c0 [ 70.853375] [ 70.853375] stack backtrace: [ 70.857860] CPU: 1 PID: 2099 Comm: syz-executor126 Not tainted 4.4.174+ #17 [ 70.864942] 0000000000000000 b142713bd09b25ca ffff8801cf2ef500 ffffffff81aad1a1 [ 70.876788] ffffffff84057a80 ffff8801d57097c0 ffffffff83a8d7f0 ffffffff83acc910 [ 70.885595] ffffffff83a8d7f0 ffff8801cf2ef550 ffffffff813abcda ffff8801cf2ef630 [ 70.893641] Call Trace: [ 70.896257] [] dump_stack+0xc1/0x120 [ 70.901642] [] print_circular_bug.cold+0x2f7/0x44e [ 70.908221] [] __lock_acquire+0x37d6/0x4f50 [ 70.914198] [] ? check_irq_usage+0xb1/0xe0 [ 70.920292] [] ? trace_hardirqs_on+0x10/0x10 [ 70.926349] [] ? trace_hardirqs_on+0x10/0x10 [ 70.932402] [] lock_acquire+0x15e/0x450 [ 70.938105] [] ? rtnl_lock+0x17/0x20 [ 70.943457] [] ? rtnl_lock+0x17/0x20 [ 70.949003] [] mutex_lock_nested+0xc1/0xb80 [ 70.955080] [] ? rtnl_lock+0x17/0x20 [ 70.960436] [] ? kvm_clock_read+0x23/0x40 [ 70.966234] [] ? kvm_clock_get_cycles+0x9/0x10 [ 70.973023] [] ? ktime_get_with_offset+0x176/0x240 [ 70.979593] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 70.986354] [] ? mutex_trylock+0x500/0x500 [ 70.992229] [] ? mark_held_locks+0xb1/0x100 [ 70.998209] [] ? __local_bh_enable_ip+0x6a/0xe0 [ 71.004528] [] rtnl_lock+0x17/0x20 [ 71.009721] [] ipv6_sock_mc_close+0x10e/0x350 [ 71.015950] [] ? fl6_free_socklist+0xb7/0x240 [ 71.022083] [] do_ipv6_setsockopt.isra.0+0x1bd1/0x30c0 [ 71.028997] [] ? ip6_ra_control+0x3c0/0x3c0 [ 71.034973] [] ? trace_hardirqs_on+0x10/0x10 [ 71.041028] [] ? tcp_v4_connect+0x1070/0x1930 [ 71.047174] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 71.053952] [] ? avc_has_perm+0x164/0x3a0 [ 71.059928] [] ? avc_has_perm+0x1d2/0x3a0 [ 71.065716] [] ? avc_has_perm+0xac/0x3a0 [ 71.071689] [] ? avc_has_perm_noaudit+0x300/0x300 [ 71.078166] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 71.084918] [] ? check_preemption_disabled+0x3c/0x200 [ 71.091756] [] ? check_preemption_disabled+0x3c/0x200 [ 71.098691] [] ? sock_has_perm+0x1c8/0x400 [ 71.104557] [] ? sock_has_perm+0x2a8/0x400 [ 71.110709] [] ? sock_has_perm+0xa6/0x400 [ 71.116502] [] ? selinux_msg_queue_alloc_security+0x2e0/0x2e0 [ 71.124038] [] ? check_preemption_disabled+0x3c/0x200 [ 71.130868] [] compat_ipv6_setsockopt+0xe7/0x1d0 [ 71.137266] [] inet_csk_compat_setsockopt+0x99/0x120 [ 71.144006] [] ? ipv6_setsockopt+0x140/0x140 [ 71.150069] [] compat_tcp_setsockopt+0x40/0x70 [ 71.156293] [] compat_sock_common_setsockopt+0xb4/0x150 [ 71.163299] [] ? do_tcp_setsockopt.isra.0+0x19a0/0x19a0 [ 71.170