[....] Starting enhanced syslogd: rsyslogd[ 13.675231] audit: type=1400 audit(1539627523.745:4): 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 '10.128.10.6' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 33.812624] [ 33.814278] ====================================================== [ 33.820570] [ INFO: possible circular locking dependency detected ] [ 33.826948] 4.4.161+ #46 Not tainted [ 33.830646] ------------------------------------------------------- [ 33.837024] syz-executor135/2072 is trying to acquire lock: [ 33.842705] (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 [ 33.850614] [ 33.850614] but task is already holding lock: [ 33.856558] (sk_lock-AF_INET6){+.+.+.}, at: [] do_ipv6_setsockopt.isra.4+0x252/0x2d50 [ 33.866671] [ 33.866671] which lock already depends on the new lock. [ 33.866671] [ 33.874958] [ 33.874958] the existing dependency chain (in reverse order) is: [ 33.882550] -> #1 (sk_lock-AF_INET6){+.+.+.}: [ 33.887691] [] lock_acquire+0x15e/0x450 [ 33.893929] [] lock_sock_nested+0xc6/0x120 [ 33.900431] [] do_ipv6_setsockopt.isra.4+0x1d2/0x2d50 [ 33.907884] [] compat_ipv6_setsockopt+0xe9/0x1d0 [ 33.914908] [] compat_udpv6_setsockopt+0x4a/0x90 [ 33.921930] [] compat_sock_common_setsockopt+0xb4/0x150 [ 33.929559] [] compat_SyS_setsockopt+0x169/0x700 [ 33.936583] [] do_fast_syscall_32+0x31e/0xa80 [ 33.943346] [] sysenter_flags_fixed+0xd/0x1a [ 33.950031] -> #0 (rtnl_mutex){+.+.+.}: [ 33.954647] [] __lock_acquire+0x3e6c/0x5f10 [ 33.961261] [] lock_acquire+0x15e/0x450 [ 33.967501] [] mutex_lock_nested+0xbb/0x8d0 [ 33.974088] [] rtnl_lock+0x17/0x20 [ 33.979899] [] ipv6_sock_mc_close+0x10e/0x350 [ 33.986661] [] do_ipv6_setsockopt.isra.4+0xd07/0x2d50 [ 33.994122] [] compat_ipv6_setsockopt+0xe9/0x1d0 [ 34.001145] [] compat_udpv6_setsockopt+0x4a/0x90 [ 34.008230] [] compat_sock_common_setsockopt+0xb4/0x150 [ 34.015875] [] compat_SyS_setsockopt+0x169/0x700 [ 34.022914] [] do_fast_syscall_32+0x31e/0xa80 [ 34.029700] [] sysenter_flags_fixed+0xd/0x1a [ 34.036375] [ 34.036375] other info that might help us debug this: [ 34.036375] [ 34.044491] Possible unsafe locking scenario: [ 34.044491] [ 34.050521] CPU0 CPU1 [ 34.055161] ---- ---- [ 34.059802] lock(sk_lock-AF_INET6); [ 34.063821] lock(rtnl_mutex); [ 34.069831] lock(sk_lock-AF_INET6); [ 34.076364] lock(rtnl_mutex); [ 34.079868] [ 34.079868] *** DEADLOCK *** [ 34.079868] [ 34.085901] 1 lock held by syz-executor135/2072: [ 34.090640] #0: (sk_lock-AF_INET6){+.+.+.}, at: [] do_ipv6_setsockopt.isra.4+0x252/0x2d50 [ 34.101275] [ 34.101275] stack backtrace: [ 34.105746] CPU: 0 PID: 2072 Comm: syz-executor135 Not tainted 4.4.161+ #46 [ 34.112832] 0000000000000000 ead0c90b65ddcef8 ffff8800b684f538 ffffffff81a9969d [ 34.120842] ffffffff83a85b10 ffffffff83ac5140 ffffffff83a85b10 ffff8801d58f88e8 [ 34.128835] ffff8801d58f8000 ffff8800b684f580 ffffffff813a856a 0000000000000001 [ 34.136831] Call Trace: [ 34.139395] [] dump_stack+0xc1/0x124 [ 34.144753] [] print_circular_bug.cold.34+0x2f7/0x432 [ 34.151570] [] __lock_acquire+0x3e6c/0x5f10 [ 34.157516] [] ? trace_hardirqs_on+0x10/0x10 [ 34.163546] [] lock_acquire+0x15e/0x450 [ 34.169146] [] ? rtnl_lock+0x17/0x20 [ 34.174484] [] ? rtnl_lock+0x17/0x20 [ 34.179822] [] mutex_lock_nested+0xbb/0x8d0 [ 34.185768] [] ? rtnl_lock+0x17/0x20 [ 34.191105] [] ? debug_lockdep_rcu_enabled+0x77/0x90 [ 34.197831] [] ? debug_lockdep_rcu_enabled+0x77/0x90 [ 34.204560] [] ? mutex_trylock+0x3e0/0x3e0 [ 34.210421] [] ? mark_held_locks+0xc7/0x130 [ 34.216378] [] ? __local_bh_enable_ip+0x6a/0xd0 [ 34.222674] [] rtnl_lock+0x17/0x20 [ 34.227840] [] ipv6_sock_mc_close+0x10e/0x350 [ 34.233959] [] ? fl6_free_socklist+0xb7/0x240 [ 34.240082] [] do_ipv6_setsockopt.isra.4+0xd07/0x2d50 [ 34.246899] [] ? ip6_ra_control+0x430/0x430 [ 34.252844] [] ? trace_hardirqs_on+0x10/0x10 [ 34.258878] [] ? __lock_acquire+0xa85/0x5f10 [ 34.264911] [] ? __local_bh_enable_ip+0x6a/0xd0 [ 34.271219] [] ? debug_lockdep_rcu_enabled+0x77/0x90 [ 34.277948] [] ? avc_has_perm+0x15a/0x3a0 [ 34.283722] [] ? avc_has_perm+0x1cc/0x3a0 [ 34.289507] [] ? avc_has_perm+0x9e/0x3a0 [ 34.295192] [] ? avc_has_perm_noaudit+0x2f0/0x2f0 [ 34.301661] [] ? check_preemption_disabled+0x3b/0x170 [ 34.308479] [] ? sock_has_perm+0x1c1/0x3f0 [ 34.314364] [] ? sock_has_perm+0x2a1/0x3f0 [ 34.320229] [] ? sock_has_perm+0x9f/0x3f0 [ 34.326001] [] ? selinux_msg_queue_alloc_security+0x2e0/0x2e0 [ 34.333512] [] ? __fget+0x12f/0x3d0 [ 34.338765] [] compat_ipv6_setsockopt+0xe9/0x1d0 [ 34.345144] [] compat_udpv6_setsockopt+0x4a/0x90 [ 34.351525] [] compat_sock_common_setsockopt+0xb4/0x150 [ 34.358511] [] ? udpv6_setsockopt+0x90/0x90 [ 34.3