[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 19.743283] random: sshd: uninitialized urandom read (32 bytes read, 31 bits of entropy available) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 24.274790] random: sshd: uninitialized urandom read (32 bytes read, 36 bits of entropy available) [ 24.628499] random: sshd: uninitialized urandom read (32 bytes read, 36 bits of entropy available) [ 25.654035] random: nonblocking pool is initialized Warning: Permanently added '10.128.0.2' (ECDSA) to the list of known hosts. 2018/06/16 05:51:31 parsed 1 programs 2018/06/16 05:51:33 executed programs: 0 [ 34.065525] IPVS: Creating netns size=2552 id=1 [ 34.303529] IPv6: ADDRCONF(NETDEV_UP): veth0_to_bridge: link is not ready [ 34.319299] IPv6: ADDRCONF(NETDEV_UP): veth1_to_bridge: link is not ready [ 34.398851] IPv6: ADDRCONF(NETDEV_UP): veth0_to_bond: link is not ready [ 34.414095] IPv6: ADDRCONF(NETDEV_UP): veth1_to_bond: link is not ready [ 34.494070] IPv6: ADDRCONF(NETDEV_UP): veth0_to_team: link is not ready [ 34.509070] IPv6: ADDRCONF(NETDEV_UP): veth1_to_team: link is not ready [ 34.526004] IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_bridge: link becomes ready [ 34.543146] IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bridge: link becomes ready [ 35.257076] IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready [ 35.299554] IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready [ 35.586014] [ 35.587679] ====================================================== [ 35.593980] [ INFO: possible circular locking dependency detected ] [ 35.600360] 4.4.137-ga2e2217 #59 Not tainted [ 35.604748] ------------------------------------------------------- [ 35.611140] syz-executor0/4060 is trying to acquire lock: [ 35.616653] (&(&q->lock)->rlock){+.-...}, at: [] ip_defrag+0x318/0x3fe0 [ 35.625518] [ 35.625518] but task is already holding lock: [ 35.631461] (_xmit_NETROM){+.-...}, at: [] sch_direct_xmit+0x23c/0x6e0 [ 35.640231] [ 35.640231] which lock already depends on the new lock. [ 35.640231] [ 35.648533] [ 35.648533] the existing dependency chain (in reverse order) is: [ 35.656136] -> #1 (_xmit_NETROM){+.-...}: [ 35.660928] [] lock_acquire+0x15e/0x450 [ 35.667282] [] _raw_spin_lock_irqsave+0x4e/0x70 [ 35.674221] [] depot_save_stack+0x211/0x610 [ 35.681177] [] save_stack+0xa9/0xd0 [ 35.687072] [] kasan_kmalloc+0xc7/0xe0 [ 35.693238] [] kasan_slab_alloc+0x12/0x20 [ 35.699667] [] kmem_cache_alloc+0xbe/0x2a0 [ 35.706171] [] inet_getpeer.part.5+0xeac/0x15a0 [ 35.713222] [] inet_getpeer+0x55b/0x6f0 [ 35.719473] [] icmp6_send+0x17c5/0x1b80 [ 35.725723] [] icmpv6_param_prob+0x29/0x40 [ 35.732226] [] ipv6_frag_rcv+0x3f94/0x4fd0 [ 35.738737] [] ip6_input_finish+0x32e/0x1550 [ 35.745417] [] ip6_input+0xf6/0x200 [ 35.751309] [] ip6_rcv_finish+0x13d/0x640 [ 35.757730] [] ipv6_rcv+0x10cb/0x1cd0 [ 35.763795] [] __netif_receive_skb_core+0x12d6/0x2940 [ 35.771271] [] __netif_receive_skb+0x5b/0x1b0 [ 35.778034] [] process_backlog+0x216/0x6a0 [ 35.784536] [] net_rx_action+0x3a2/0xdb0 [ 35.790878] [] __do_softirq+0x22c/0xa1a [ 35.797128] [] do_softirq_own_stack+0x1c/0x30 [ 35.803922] [] do_softirq.part.16+0x54/0x60 [ 35.810508] [] do_softirq+0x19/0x20 [ 35.816422] [] netif_rx_ni+0xec/0x3a0 [ 35.822759] [] tun_get_user+0xbe7/0x2410 [ 35.829108] [] tun_chr_write_iter+0xd5/0x190 [ 35.835797] [] do_iter_readv_writev+0x13c/0x1e0 [ 35.842734] [] compat_do_readv_writev+0x2e2/0x6e0 [ 35.849857] [] compat_writev+0xe1/0x150 [ 35.856106] [] compat_SyS_writev+0xd8/0x1c0 [ 35.862704] [] do_fast_syscall_32+0x326/0x8b0 [ 35.869465] [] sysenter_flags_fixed+0xd/0x17 [ 35.876151] -> #0 (&(&q->lock)->rlock){+.-...}: [ 35.881451] [] __lock_acquire+0x3902/0x5270 [ 35.888038] [] lock_acquire+0x15e/0x450 [ 35.894281] [] _raw_spin_lock+0x36/0x50 [ 35.900530] [] ip_defrag+0x318/0x3fe0 [ 35.906611] [] ip_check_defrag+0x3c8/0x7e0 [ 35.913121] [] packet_rcv_fanout+0x52a/0x5e0 [ 35.919812] [] dev_hard_start_xmit+0x644/0x11c0 [ 35.926768] [] sch_direct_xmit+0x2c1/0x6e0 [ 35.933271] [] __dev_queue_xmit+0xef3/0x1c80 [ 35.939954] [] dev_queue_xmit+0x17/0x20 [ 35.946196] [] neigh_resolve_output+0x637/0x790 [ 35.953130] [] ip_finish_output2+0x6ab/0x1110 [ 35.959903] [] ip_do_fragment+0x19cc/0x2190 [ 35.966489] [] ip_fragment.constprop.51+0x143/0x200 [ 35.973795] [] ip_finish_output+0x48a/0xc00 [ 35.980384] [] ip_mc_output+0x233/0x980 [ 35.986661] [] ip_local_out+0x9b/0x180 [ 35.992824] [] ip_send_skb+0x3c/0xc0 [ 35.998812] [] udp_send_skb+0x5c3/0xc60 [ 36.005061] [] udp_sendmsg+0x16c9/0x1c70 [ 36.011478] [] inet_sendmsg+0x203/0x4d0 [ 36.017729] [] sock_sendmsg+0xcc/0x110 [ 36.023889] [] SYSC_sendto+0x21c/0x370 [ 36.030068] [] SyS_sendto+0x40/0x50 [ 36.035975] [] do_fast_syscall_32+0x326/0x8b0 [ 36.042756] [] sysenter_flags_fixed+0xd/0x17 [ 36.049437] [ 36.049437] other info that might help us debug this: [ 36.049437] [ 36.057552] Possible unsafe locking scenario: [ 36.057552] [ 36.063583] CPU0 CPU1 [ 36.068220] ---- ---- [ 36.072863] lock(_xmit_NETROM); [ 36.076541] lock(&(&q->lock)->rlock); [ 36.083439] lock(_xmit_NETROM); [ 36.089711] lock(&(&q->lock)->rlock); [ 36.093906] [ 36.093906] *** DEADLOCK *** [ 36.093906] [ 36.099940] 4 locks held by syz-executor0/4060: [ 36.104587] #0: (rcu_read_lock_bh){......}, at: [] ip_finish_output2+0x212/0x1110 [ 36.114547] #1: (rcu_read_lock_bh){......}, at: [] __dev_queue_xmit+0x1d7/0x1c80 [ 36.124416] #2: (_xmit_NETROM){+.-...}, at: [] sch_direct_xmit+0x23c/0x6e0 [ 36.133747] #3: (rcu_read_lock){......}, at: [] dev_hard_start_xmit+0xa8/0x11c0 [ 36.143528] [ 36.143528] stack backtrace: [ 36.148001] CPU: 1 PID: 4060 Comm: syz-executor0 Not tainted 4.4.137-ga2e2217 #59 [ 36.155597] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 36.164935] 0000000000000000 54302b7d1e45a49a ffff8801d96becc8 ffffffff81e0ee0d [ 36.172947] ffffffff853ed070 ffffffff853ebc30 ffffffff853ed070 ffff8800bac68950 [ 36.180989] ffff8800bac68000 ffff8801d96bed10 ffffffff8140e6ab 0000000000000003 [ 36.189002] Call Trace: [ 36.191570] [] dump_stack+0xc1/0x124 [ 36.196916] [] print_circular_bug.cold.50+0x1bd/0x27d [ 36.203736] [] __lock_acquire+0x3902/0x5270 [ 36.209683] [] ? debug_check_no_locks_freed+0x210/0x210 [ 36.216678] [] ? trace_hardirqs_on_caller+0x266/0x590 [ 36.223497] [] lock_acquire+0x15e/0x450 [ 36.229098] [] ? ip_defrag+0x318/0x3fe0 [ 36.234696] [] ? inet_frag_find+0x22e/0x9c0 [ 36.240644] [] _raw_spin_lock+0x36/0x50 [ 36.246246] [] ? ip_defrag+0x318/0x3fe0 [ 36.251860] [] ip_defrag+0x318/0x3fe0 [ 36.257304] [] ? debug_check_no_locks_freed+0x210/0x210 [ 36.264308] [] ? memcpy+0x45/0x50 [ 36.269410] [] ? ip_expire+0x770/0x770 [ 36.274923] [] ip_check_defrag+0x3c8/0x7e0 [ 36.280885] [] ? ip_defrag+0x3fe0/0x3fe0 [ 36.286584] [] packet_rcv_fanout+0x52a/0x5e0 [ 36.292622] [] ? packet_bind+0x190/0x190 [ 36.298318] [] dev_hard_start_xmit+0x644/0x11c0 [ 36.304611] [] ? dev_hard_start_xmit+0xa8/0x11c0 [ 36.311002] [] sch_direct_xmit+0x2c1/0x6e0 [ 36.316874] [] ? dev_watchdog+0x7f0/0x7f0 [ 36.322650] [] __dev_queue_xmit+0xef3/0x1c80 [ 36.328690] [] ? __dev_queue_xmit+0x1d7/0x1c80 [ 36.334905] [] ? debug_check_no_locks_freed+0x210/0x210 [ 36.341893] [] ? netdev_pick_tx+0x2c0/0x2c0 [ 36.347847] [] ? memcpy+0x45/0x50 [ 36.352925] [] dev_queue_xmit+0x17/0x20 [ 36.358533] [] neigh_resolve_output+0x637/0x790 [ 36.364825] [] ? ip_finish_output2+0x6ab/0x1110 [ 36.371135] [] ip_finish_output2+0x6ab/0x1110 [ 36.377262] [] ? ip_finish_output2+0x212/0x1110 [ 36.383556] [] ? nf_ct_deliver_cached_events+0x335/0x560 [ 36.390636] [] ? nf_ct_deliver_cached_events+0x83/0x560 [ 36.397623] [] ? ip_copy_metadata+0x700/0x700 [ 36.403746] [] ? ip_options_fragment+0x1ac/0x280 [ 36.410125] [] ip_do_fragment+0x19cc/0x2190 [ 36.416073] [] ? ip_copy_metadata+0x700/0x700 [ 36.422193] [] ip_fragment.constprop.51+0x143/0x200 [ 36.428839] [] ip_finish_output+0x48a/0xc00 [ 36.434785] [] ip_mc_output+0x233/0x980 [ 36.440389] [] ? ip_queue_xmit+0x1af0/0x1af0 [ 36.446432] [] ? ip_make_skb+0x116/0x210 [ 36.452116] [] ? ip_fragment.constprop.51+0x200/0x200 [ 36.458931] [] ? ip_flush_pending_frames+0x30/0x30 [ 36.465494] [] ip_local_out+0x9b/0x180 [ 36.471014] [] ip_send_skb+0x3c/0xc0 [ 36.476535] [] udp_send_skb+0x5c3/0xc60 [ 36.482146] [] udp_sendmsg+0x16c9/0x1c70 [ 36.487831] [] ? ip_reply_glue_bits+0xc0/0xc0 [ 36.493959] [] ? udp4_lib_lookup+0x60/0x60 [ 36.499821] [] ? debug_check_no_locks_freed+0x210/0x210 [ 36.506820] [] ? sock_has_perm+0x1c1/0x400 [ 36.512678] [] ? sock_has_perm+0x29f/0x400 [ 36.518557] [] ? sock_has_perm+0x9f/0x400 [ 36.524336] [] ? inet_sendmsg+0x143/0x4d0 [ 36.530119] [] inet_sendmsg+0x203/0x4d0 [ 36.535736] [] ? inet_sendmsg+0x73/0x4d0 [ 36.541437] [] ? inet_recvmsg+0x4c0/0x4c0 [ 36.547226] [] sock_sendmsg+0xcc/0x110 [ 36.552739] [] SYSC_sendto+0x21c/0x370 [ 36.558265] [] ? SYSC_connect+0x300/0x300 [ 36.564052] [] ? native_set_pte_at+0xe0/0xe0 [ 36.570090] [] ? do_huge_pmd_anonymous_page+0x737/0x9d0 [ 36.577082] [] ? _raw_spin_unlock+0x2c/0x50 [ 36.583030] [] ? compat_SyS_futex+0x1e1/0x2f0 [ 36.589158]