[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 22.223566] random: sshd: uninitialized urandom read (32 bytes read, 32 bits of entropy available) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 26.689685] random: sshd: uninitialized urandom read (32 bytes read, 40 bits of entropy available) [ 27.222597] random: sshd: uninitialized urandom read (32 bytes read, 40 bits of entropy available) [ 28.560896] random: sshd: uninitialized urandom read (32 bytes read, 117 bits of entropy available) [ 28.719547] random: sshd: uninitialized urandom read (32 bytes read, 119 bits of entropy available) Warning: Permanently added '10.128.0.20' (ECDSA) to the list of known hosts. [ 34.122759] random: sshd: uninitialized urandom read (32 bytes read, 123 bits of entropy available) 2018/05/30 22:00:16 parsed 1 programs 2018/05/30 22:00:16 executed programs: 0 [ 34.659171] IPVS: Creating netns size=2552 id=1 [ 34.898160] IPv6: ADDRCONF(NETDEV_UP): veth0_to_bridge: link is not ready [ 34.913006] IPv6: ADDRCONF(NETDEV_UP): veth1_to_bridge: link is not ready [ 34.993853] IPv6: ADDRCONF(NETDEV_UP): veth0_to_bond: link is not ready [ 35.009177] IPv6: ADDRCONF(NETDEV_UP): veth1_to_bond: link is not ready [ 35.089144] IPv6: ADDRCONF(NETDEV_UP): veth0_to_team: link is not ready [ 35.104750] IPv6: ADDRCONF(NETDEV_UP): veth1_to_team: link is not ready [ 35.121941] IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_bridge: link becomes ready [ 35.139797] IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bridge: link becomes ready [ 35.888194] IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready [ 35.927645] IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready [ 36.222003] [ 36.223660] ====================================================== [ 36.229958] [ INFO: possible circular locking dependency detected ] [ 36.236355] 4.4.134-gcb3afe1 #51 Not tainted [ 36.240737] ------------------------------------------------------- [ 36.247125] syz-executor0/4212 is trying to acquire lock: [ 36.252639] (&(&q->lock)->rlock){+.-...}, at: [] ip_defrag+0x318/0x3fe0 [ 36.261524] [ 36.261524] but task is already holding lock: [ 36.267481] (_xmit_NETROM){+.-...}, at: [] sch_direct_xmit+0x23c/0x6e0 [ 36.276324] [ 36.276324] which lock already depends on the new lock. [ 36.276324] [ 36.284620] [ 36.284620] the existing dependency chain (in reverse order) is: [ 36.292239] -> #1 (_xmit_NETROM){+.-...}: [ 36.297084] [] lock_acquire+0x15e/0x450 [ 36.303365] [] _raw_spin_lock_irqsave+0x4e/0x70 [ 36.310317] [] depot_save_stack+0x211/0x610 [ 36.316913] [] save_stack+0xa9/0xd0 [ 36.322818] [] kasan_kmalloc+0xc7/0xe0 [ 36.328974] [] kasan_slab_alloc+0x12/0x20 [ 36.335391] [] kmem_cache_alloc+0xbe/0x2a0 [ 36.341904] [] inet_getpeer.part.5+0xeac/0x15a0 [ 36.348872] [] inet_getpeer+0x55b/0x6f0 [ 36.355120] [] icmp6_send+0x17c5/0x1b80 [ 36.361368] [] icmpv6_param_prob+0x29/0x40 [ 36.367892] [] ipv6_frag_rcv+0x3f94/0x4fd0 [ 36.374410] [] ip6_input_finish+0x32e/0x1550 [ 36.381093] [] ip6_input+0xf6/0x200 [ 36.386998] [] ip6_rcv_finish+0x13d/0x640 [ 36.393439] [] ipv6_rcv+0x10cb/0x1cd0 [ 36.399541] [] __netif_receive_skb_core+0x12d6/0x2940 [ 36.407007] [] __netif_receive_skb+0x5b/0x1b0 [ 36.413776] [] process_backlog+0x216/0x6a0 [ 36.420277] [] net_rx_action+0x3a2/0xdb0 [ 36.426604] [] __do_softirq+0x22c/0xa1a [ 36.432863] [] do_softirq_own_stack+0x1c/0x30 [ 36.439637] [] do_softirq.part.16+0x54/0x60 [ 36.446244] [] do_softirq+0x19/0x20 [ 36.452142] [] netif_rx_ni+0xec/0x3a0 [ 36.458222] [] tun_get_user+0xbe7/0x2410 [ 36.464572] [] tun_chr_write_iter+0xd5/0x190 [ 36.471261] [] do_iter_readv_writev+0x13c/0x1e0 [ 36.478210] [] compat_do_readv_writev+0x2e2/0x6e0 [ 36.485333] [] compat_writev+0xe1/0x150 [ 36.491581] [] compat_SyS_writev+0xd8/0x1c0 [ 36.498176] [] do_fast_syscall_32+0x326/0x8b0 [ 36.504956] [] sysenter_flags_fixed+0xd/0x17 [ 36.511640] -> #0 (&(&q->lock)->rlock){+.-...}: [ 36.516947] [] __lock_acquire+0x3902/0x5270 [ 36.523542] [] lock_acquire+0x15e/0x450 [ 36.529792] [] _raw_spin_lock+0x36/0x50 [ 36.536053] [] ip_defrag+0x318/0x3fe0 [ 36.542137] [] ip_check_defrag+0x3c8/0x7e0 [ 36.548644] [] packet_rcv_fanout+0x52a/0x5e0 [ 36.555332] [] dev_hard_start_xmit+0x644/0x11c0 [ 36.562471] [] sch_direct_xmit+0x2c1/0x6e0 [ 36.568978] [] __dev_queue_xmit+0xef3/0x1c80 [ 36.575675] [] dev_queue_xmit+0x17/0x20 [ 36.581926] [] neigh_resolve_output+0x637/0x790 [ 36.588886] [] ip_finish_output2+0x6ab/0x1110 [ 36.595664] [] ip_do_fragment+0x19cc/0x2190 [ 36.602286] [] ip_fragment.constprop.51+0x143/0x200 [ 36.609583] [] ip_finish_output+0x48a/0xc00 [ 36.616187] [] ip_mc_output+0x233/0x980 [ 36.622451] [] ip_local_out+0x9b/0x180 [ 36.628607] [] ip_send_skb+0x3c/0xc0 [ 36.634603] [] udp_send_skb+0x5c3/0xc60 [ 36.640866] [] udp_sendmsg+0x16c9/0x1c70 [ 36.647195] [] inet_sendmsg+0x203/0x4d0 [ 36.653444] [] sock_sendmsg+0xcc/0x110 [ 36.659638] [] SYSC_sendto+0x21c/0x370 [ 36.665814] [] SyS_sendto+0x40/0x50 [ 36.671718] [] do_fast_syscall_32+0x326/0x8b0 [ 36.678641] [] sysenter_flags_fixed+0xd/0x17 [ 36.685342] [ 36.685342] other info that might help us debug this: [ 36.685342] [ 36.693465] Possible unsafe locking scenario: [ 36.693465] [ 36.699499] CPU0 CPU1 [ 36.704140] ---- ---- [ 36.708791] lock(_xmit_NETROM); [ 36.712462] lock(&(&q->lock)->rlock); [ 36.719165] lock(_xmit_NETROM); [ 36.725362] lock(&(&q->lock)->rlock); [ 36.729560] [ 36.729560] *** DEADLOCK *** [ 36.729560] [ 36.735596] 4 locks held by syz-executor0/4212: [ 36.740246] #0: (rcu_read_lock_bh){......}, at: [] ip_finish_output2+0x212/0x1110 [ 36.750200] #1: (rcu_read_lock_bh){......}, at: [] __dev_queue_xmit+0x1d7/0x1c80 [ 36.760071] #2: (_xmit_NETROM){+.-...}, at: [] sch_direct_xmit+0x23c/0x6e0 [ 36.769428] #3: (rcu_read_lock){......}, at: [] dev_hard_start_xmit+0xa8/0x11c0 [ 36.779234] [ 36.779234] stack backtrace: [ 36.783707] CPU: 1 PID: 4212 Comm: syz-executor0 Not tainted 4.4.134-gcb3afe1 #51 [ 36.791391] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 36.800725] 0000000000000000 159d4b633c7be5e4 ffff8801d71c6cc8 ffffffff81e0f02d [ 36.808750] ffffffff853ecd10 ffffffff853eba80 ffffffff853ecd10 ffff8801d6d9d150 [ 36.816747] ffff8801d6d9c800 ffff8801d71c6d10 ffffffff8140e62b 0000000000000003 [ 36.824764] Call Trace: [ 36.827334] [] dump_stack+0xc1/0x124 [ 36.832676] [] print_circular_bug.cold.50+0x1bd/0x27d [ 36.839496] [] __lock_acquire+0x3902/0x5270 [ 36.845450] [] ? debug_check_no_locks_freed+0x210/0x210 [ 36.852444] [] ? trace_hardirqs_on_caller+0x266/0x590 [ 36.859263] [] lock_acquire+0x15e/0x450 [ 36.864877] [] ? ip_defrag+0x318/0x3fe0 [ 36.870491] [] ? inet_frag_find+0x22e/0x9c0 [ 36.876441] [] _raw_spin_lock+0x36/0x50 [ 36.882060] [] ? ip_defrag+0x318/0x3fe0 [ 36.887667] [] ip_defrag+0x318/0x3fe0 [ 36.893101] [] ? debug_check_no_locks_freed+0x210/0x210 [ 36.900102] [] ? memcpy+0x45/0x50 [ 36.905185] [] ? ip_expire+0x770/0x770 [ 36.910707] [] ip_check_defrag+0x3c8/0x7e0 [ 36.916573] [] ? ip_defrag+0x3fe0/0x3fe0 [ 36.922266] [] packet_rcv_fanout+0x52a/0x5e0 [ 36.928309] [] ? packet_bind+0x190/0x190 [ 36.934006] [] dev_hard_start_xmit+0x644/0x11c0 [ 36.940317] [] ? dev_hard_start_xmit+0xa8/0x11c0 [ 36.946720] [] sch_direct_xmit+0x2c1/0x6e0 [ 36.952589] [] ? dev_watchdog+0x7f0/0x7f0 [ 36.958383] [] __dev_queue_xmit+0xef3/0x1c80 [ 36.964425] [] ? __dev_queue_xmit+0x1d7/0x1c80 [ 36.970660] [] ? debug_check_no_locks_freed+0x210/0x210 [ 36.977659] [] ? netdev_pick_tx+0x2c0/0x2c0 [ 36.983655] [] ? memcpy+0x45/0x50 [ 36.988743] [] dev_queue_xmit+0x17/0x20 [ 36.994353] [] neigh_resolve_output+0x637/0x790 [ 37.000658] [] ? ip_finish_output2+0x6ab/0x1110 [ 37.006964] [] ip_finish_output2+0x6ab/0x1110 [ 37.013324] [] ? ip_finish_output2+0x212/0x1110 [ 37.019631] [] ? nf_ct_deliver_cached_events+0x335/0x560 [ 37.026852] [] ? nf_ct_deliver_cached_events+0x83/0x560 [ 37.033852] [] ? ip_copy_metadata+0x700/0x700 [ 37.039981] [] ? ip_options_fragment+0x1ac/0x280 [ 37.046368] [] ip_do_fragment+0x19cc/0x2190 [ 37.052336] [] ? ip_copy_metadata+0x700/0x700 [ 37.058486] [] ip_fragment.constprop.51+0x143/0x200 [ 37.065157] [] ip_finish_output+0x48a/0xc00 [ 37.071115] [] ip_mc_output+0x233/0x980 [ 37.076724] [] ? ip_queue_xmit+0x1af0/0x1af0 [ 37.082762] [] ? ip_make_skb+0x116/0x210 [ 37.088540] [] ? ip_fragment.constprop.51+0x200/0x200 [ 37.095360] [] ? ip_flush_pending_frames+0x30/0x30 [ 37.101928] [] ip_local_out+0x9b/0x180 [ 37.107464] [] ip_send_skb+0x3c/0xc0 [ 37.112833] [] udp_send_skb+0x5c3/0xc60 [ 37.118444] [] udp_sendmsg+0x16c9/0x1c70 [ 37.124156] [] ? ip_reply_glue_bits+0xc0/0xc0 [ 37.130553] [] ? udp4_lib_lookup+0x60/0x60 [ 37.136455] [] ? debug_check_no_locks_freed+0x210/0x210 [ 37.143464] [] ? sock_has_perm+0x1c1/0x400 [ 37.149341] [] ? sock_has_perm+0x29f/0x400 [ 37.155225] [] ? sock_has_perm+0x9f/0x400 [ 37.161023] [] ? inet_sendmsg+0x143/0x4d0 [ 37.166811] [] inet_sendmsg+0x203/0x4d0 [ 37.172418] [] ? inet_sendmsg+0x73/0x4d0 [ 37.178110] [] ? inet_recvmsg+0x4c0/0x4c0 [ 37.183890] [] sock_sendmsg+0xcc/0x110 [ 37.189421] [] SYSC_sendto+0x21c/0x370 [ 37.194943] [] ? SYSC_connect+0x300/0x300 [ 37.200750] [] ? native_set_pte_at+0xe0/0xe0 [ 37.206810] [] ? do_huge_pmd_anonymous_page+0x737/0x9d0 [ 37.213807] [] ? _raw_spin_unlock+0x2c/0x50 [ 37.219767] [] ? compat_SyS_futex+0x1e1/0x2f0 [ 37.22