[....] Starting enhanced syslogd: rsyslogd[ 13.638090] audit: type=1400 audit(1540808433.572:4): avc: denied { syslog } for pid=1917 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[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. Starting mcstransd: [....] Starting file context maintaining daemon: restorecond[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.89' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 36.622040] [ 36.623683] ====================================================== [ 36.629972] [ INFO: possible circular locking dependency detected ] [ 36.636347] 4.4.162+ #117 Not tainted [ 36.640113] ------------------------------------------------------- [ 36.646646] syz-executor528/2076 is trying to acquire lock: [ 36.652326] (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 [ 36.660246] [ 36.660246] but task is already holding lock: [ 36.666194] (sk_lock-AF_INET6){+.+.+.}, at: [] do_ipv6_setsockopt.isra.4+0x252/0x2d50 [ 36.676290] [ 36.676290] which lock already depends on the new lock. [ 36.676290] [ 36.684679] [ 36.684679] the existing dependency chain (in reverse order) is: [ 36.692377] -> #1 (sk_lock-AF_INET6){+.+.+.}: [ 36.697523] [] lock_acquire+0x15e/0x450 [ 36.703767] [] lock_sock_nested+0xc6/0x120 [ 36.710284] [] do_ipv6_setsockopt.isra.4+0x1d2/0x2d50 [ 36.717739] [] ipv6_setsockopt+0x97/0x130 [ 36.724167] [] udpv6_setsockopt+0x4a/0x90 [ 36.730584] [] sock_common_setsockopt+0x9a/0xe0 [ 36.737760] [] SyS_setsockopt+0x166/0x260 [ 36.744170] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 36.751867] -> #0 (rtnl_mutex){+.+.+.}: [ 36.756577] [] __lock_acquire+0x3e6c/0x5f10 [ 36.763172] [] lock_acquire+0x15e/0x450 [ 36.769422] [] mutex_lock_nested+0xbb/0x8d0 [ 36.776027] [] rtnl_lock+0x17/0x20 [ 36.781842] [] ipv6_sock_mc_close+0x10e/0x350 [ 36.788605] [] do_ipv6_setsockopt.isra.4+0xd07/0x2d50 [ 36.796158] [] ipv6_setsockopt+0x97/0x130 [ 36.802591] [] udpv6_setsockopt+0x4a/0x90 [ 36.809019] [] sock_common_setsockopt+0x9a/0xe0 [ 36.816308] [] SyS_setsockopt+0x166/0x260 [ 36.822813] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 36.830012] [ 36.830012] other info that might help us debug this: [ 36.830012] [ 36.838123] Possible unsafe locking scenario: [ 36.838123] [ 36.844154] CPU0 CPU1 [ 36.848886] ---- ---- [ 36.853721] lock(sk_lock-AF_INET6); [ 36.857762] lock(rtnl_mutex); [ 36.863784] lock(sk_lock-AF_INET6); [ 36.870461] lock(rtnl_mutex); [ 36.873959] [ 36.873959] *** DEADLOCK *** [ 36.873959] [ 36.879993] 1 lock held by syz-executor528/2076: [ 36.884719] #0: (sk_lock-AF_INET6){+.+.+.}, at: [] do_ipv6_setsockopt.isra.4+0x252/0x2d50 [ 36.895463] [ 36.895463] stack backtrace: [ 36.899948] CPU: 0 PID: 2076 Comm: syz-executor528 Not tainted 4.4.162+ #117 [ 36.907105] 0000000000000000 d7479cde9f4cf5ff ffff8801d3d3f5a8 ffffffff81a994bd [ 36.915183] ffffffff83a85960 ffffffff83ac48d0 ffffffff83a85960 ffff8800b7cab868 [ 36.923181] ffff8800b7caaf80 ffff8801d3d3f5f0 ffffffff813a834a 0000000000000001 [ 36.931414] Call Trace: [ 36.933987] [] dump_stack+0xc1/0x124 [ 36.939332] [] print_circular_bug.cold.34+0x2f7/0x432 [ 36.946308] [] __lock_acquire+0x3e6c/0x5f10 [ 36.952265] [] ? trace_hardirqs_on+0x10/0x10 [ 36.958300] [] lock_acquire+0x15e/0x450 [ 36.964029] [] ? rtnl_lock+0x17/0x20 [ 36.969367] [] ? rtnl_lock+0x17/0x20 [ 36.974709] [] mutex_lock_nested+0xbb/0x8d0 [ 36.980662] [] ? rtnl_lock+0x17/0x20 [ 36.986002] [] ? debug_lockdep_rcu_enabled+0x77/0x90 [ 36.992732] [] ? mutex_trylock+0x3e0/0x3e0 [ 36.998718] [] ? mark_held_locks+0xc7/0x130 [ 37.004669] [] ? __local_bh_enable_ip+0x6a/0xd0 [ 37.010960] [] rtnl_lock+0x17/0x20 [ 37.016126] [] ipv6_sock_mc_close+0x10e/0x350 [ 37.022246] [] ? fl6_free_socklist+0xb7/0x240 [ 37.028364] [] do_ipv6_setsockopt.isra.4+0xd07/0x2d50 [ 37.035174] [] ? ip6_ra_control+0x430/0x430 [ 37.041185] [] ? trace_hardirqs_on+0x10/0x10 [ 37.047245] [] ? __lock_acquire+0xa85/0x5f10 [ 37.053304] [] ? __local_bh_enable_ip+0x6a/0xd0 [ 37.059602] [] ? debug_lockdep_rcu_enabled+0x77/0x90 [ 37.066418] [] ? avc_has_perm+0x15a/0x3a0 [ 37.072192] [] ? avc_has_perm+0x1cc/0x3a0 [ 37.077964] [] ? avc_has_perm+0x9e/0x3a0 [ 37.083648] [] ? avc_has_perm_noaudit+0x2f0/0x2f0 [ 37.090119] [] ? check_preemption_disabled+0x3b/0x170 [ 37.096989] [] ? sock_has_perm+0x1c1/0x3f0 [ 37.102876] [] ? sock_has_perm+0x2a1/0x3f0 [ 37.108741] [] ? sock_has_perm+0x9f/0x3f0 [ 37.114525] [] ? selinux_msg_queue_alloc_security+0x2e0/0x2e0 [ 37.122041] [] ? ip6_datagram_connect+0x3a/0x50 [ 37.128343] [] ipv6_setsockopt+0x97/0x130 [ 37.134128] [] udpv6_setsockopt+0x4a/0x90 [ 37.139921] [] sock_common_setsockopt+0x9a/0xe0 [ 37.146232] [] SyS_setsockopt+0x166/0x260 [ 37.152013] [] ? SyS_recv+0x40/0x40 [ 37.157267] [] ? retint_user+0x18/0x3c [ 37.162784] [] ? lockdep_sys_exit_thunk+0x12/0x14 [ 37.169262] [] entry_SYSCALL_64_fastpa