[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 19.596223] random: sshd: uninitialized urandom read (32 bytes read, 33 bits of entropy available) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 23.611814] random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available) [ 23.911794] random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available) [ 25.191556] random: sshd: uninitialized urandom read (32 bytes read, 110 bits of entropy available) [ 25.344065] random: sshd: uninitialized urandom read (32 bytes read, 113 bits of entropy available) Warning: Permanently added '10.128.10.49' (ECDSA) to the list of known hosts. [ 30.774898] random: sshd: uninitialized urandom read (32 bytes read, 117 bits of entropy available) 2018/07/14 06:46:01 parsed 1 programs [ 32.388934] random: cc1: uninitialized urandom read (8 bytes read, 119 bits of entropy available) 2018/07/14 06:46:03 executed programs: 0 [ 33.500681] IPVS: Creating netns size=2552 id=1 [ 33.610593] [ 33.612269] ====================================================== [ 33.618577] [ INFO: possible circular locking dependency detected ] [ 33.624955] 4.4.140-ged9bdc8 #4 Not tainted [ 33.630115] ------------------------------------------------------- [ 33.636494] syz-executor0/3850 is trying to acquire lock: [ 33.642011] (&(&q->lock)->rlock){+.-...}, at: [] ip_defrag+0x318/0x3fe0 [ 33.650903] [ 33.650903] but task is already holding lock: [ 33.656844] (_xmit_NETROM){+.-...}, at: [] sch_direct_xmit+0x23c/0x6e0 [ 33.665614] [ 33.665614] which lock already depends on the new lock. [ 33.665614] [ 33.673898] [ 33.673898] the existing dependency chain (in reverse order) is: [ 33.681488] -> #1 (_xmit_NETROM){+.-...}: [ 33.686259] [] lock_acquire+0x15e/0x450 [ 33.692514] [] _raw_spin_lock_irqsave+0x4e/0x70 [ 33.699471] [] depot_save_stack+0x211/0x610 [ 33.706067] [] save_stack+0xa9/0xd0 [ 33.711986] [] kasan_kmalloc+0xc7/0xe0 [ 33.718147] [] kasan_slab_alloc+0x12/0x20 [ 33.724566] [] kmem_cache_alloc+0xbe/0x2a0 [ 33.731060] [] inet_getpeer.part.5+0xeac/0x15a0 [ 33.737994] [] inet_getpeer+0x55b/0x6f0 [ 33.744229] [] icmp6_send+0x17c5/0x1b80 [ 33.750469] [] icmpv6_param_prob+0x29/0x40 [ 33.756965] [] ipv6_frag_rcv+0x3f94/0x4fd0 [ 33.763461] [] ip6_input_finish+0x32e/0x1550 [ 33.770130] [] ip6_input+0xf6/0x200 [ 33.776031] [] ip6_rcv_finish+0x13d/0x640 [ 33.782443] [] ipv6_rcv+0x10cb/0x1cd0 [ 33.788527] [] __netif_receive_skb_core+0x12d6/0x2940 [ 33.795991] [] __netif_receive_skb+0x5b/0x1b0 [ 33.802749] [] process_backlog+0x216/0x6a0 [ 33.809246] [] net_rx_action+0x3a2/0xdb0 [ 33.815585] [] __do_softirq+0x22c/0xa1a [ 33.821839] [] do_softirq_own_stack+0x1c/0x30 [ 33.828618] [] do_softirq.part.16+0x54/0x60 [ 33.835213] [] do_softirq+0x19/0x20 [ 33.841118] [] netif_rx_ni+0xec/0x3a0 [ 33.847223] [] tun_get_user+0xbe7/0x2410 [ 33.853556] [] tun_chr_write_iter+0xd5/0x190 [ 33.860236] [] do_iter_readv_writev+0x13c/0x1e0 [ 33.867167] [] compat_do_readv_writev+0x2e2/0x6e0 [ 33.874272] [] compat_writev+0xe1/0x150 [ 33.880520] [] compat_SyS_writev+0xd8/0x1c0 [ 33.887102] [] do_fast_syscall_32+0x326/0x8b0 [ 33.893858] [] sysenter_flags_fixed+0xd/0x17 [ 33.900542] -> #0 (&(&q->lock)->rlock){+.-...}: [ 33.905830] [] __lock_acquire+0x3902/0x5270 [ 33.912416] [] lock_acquire+0x15e/0x450 [ 33.918652] [] _raw_spin_lock+0x36/0x50 [ 33.924886] [] ip_defrag+0x318/0x3fe0 [ 33.930949] [] ip_check_defrag+0x3c8/0x7e0 [ 33.937453] [] packet_rcv_fanout+0x52a/0x5e0 [ 33.944137] [] dev_hard_start_xmit+0x644/0x11c0 [ 33.951076] [] sch_direct_xmit+0x2c1/0x6e0 [ 33.957599] [] __dev_queue_xmit+0xef3/0x1c80 [ 33.964278] [] dev_queue_xmit+0x17/0x20 [ 33.970546] [] neigh_resolve_output+0x637/0x790 [ 33.977484] [] ip_finish_output2+0x6ab/0x1110 [ 33.984238] [] ip_do_fragment+0x19cc/0x2190 [ 33.990828] [] ip_fragment.constprop.51+0x143/0x200 [ 33.998124] [] ip_finish_output+0x48a/0xc00 [ 34.004705] [] ip_mc_output+0x233/0x980 [ 34.010948] [] ip_local_out+0x9b/0x180 [ 34.017100] [] ip_send_skb+0x3c/0xc0 [ 34.023100] [] udp_send_skb+0x5c3/0xc60 [ 34.029350] [] udp_sendmsg+0x16c9/0x1c70 [ 34.035675] [] inet_sendmsg+0x203/0x4d0 [ 34.041936] [] sock_sendmsg+0xcc/0x110 [ 34.048086] [] SYSC_sendto+0x21c/0x370 [ 34.054343] [] SyS_sendto+0x40/0x50 [ 34.060239] [] do_fast_syscall_32+0x326/0x8b0 [ 34.067007] [] sysenter_flags_fixed+0xd/0x17 [ 34.073678] [ 34.073678] other info that might help us debug this: [ 34.073678] [ 34.081790] Possible unsafe locking scenario: [ 34.081790] [ 34.087835] CPU0 CPU1 [ 34.092481] ---- ---- [ 34.097119] lock(_xmit_NETROM); [ 34.100783] lock(&(&q->lock)->rlock); [ 34.107480] lock(_xmit_NETROM); [ 34.113671] lock(&(&q->lock)->rlock); [ 34.117858] [ 34.117858] *** DEADLOCK *** [ 34.117858] [ 34.123900] 4 locks held by syz-executor0/3850: [ 34.128545] #0: (rcu_read_lock_bh){......}, at: [] ip_finish_output2+0x212/0x1110 [ 34.138504] #1: (rcu_read_lock_bh){......}, at: [] __dev_queue_xmit+0x1d7/0x1c80 [ 34.148371] #2: (_xmit_NETROM){+.-...}, at: [] sch_direct_xmit+0x23c/0x6e0 [ 34.157716] #3: (rcu_read_lock){......}, at: [] dev_hard_start_xmit+0xa8/0x11c0 [ 34.167490] [ 34.167490] stack backtrace: [ 34.171967] CPU: 0 PID: 3850 Comm: syz-executor0 Not tainted 4.4.140-ged9bdc8 #4 [ 34.179485] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 34.188823] 0000000000000000 2ac34a5216a5e810 ffff8801d8f36cc8 ffffffff81e0e08d [ 34.196833] ffffffff853ec2b0 ffffffff853ebbf0 ffffffff853ec2b0 ffff8801c870a150 [ 34.204826] ffff8801c8709800 ffff8801d8f36d10 ffffffff8140e6eb 0000000000000003 [ 34.212822] Call Trace: [ 34.215385] [] dump_stack+0xc1/0x124 [ 34.220732] [] print_circular_bug.cold.50+0x1bd/0x27d [ 34.227546] [] __lock_acquire+0x3902/0x5270 [ 34.233498] [] ? debug_check_no_locks_freed+0x210/0x210 [ 34.240493] [] ? trace_hardirqs_on_caller+0x266/0x590 [ 34.247309] [] lock_acquire+0x15e/0x450 [ 34.252921] [] ? ip_defrag+0x318/0x3fe0 [ 34.258525] [] ? inet_frag_find+0x22e/0x9c0 [ 34.264472] [] _raw_spin_lock+0x36/0x50 [ 34.270075] [] ? ip_defrag+0x318/0x3fe0 [ 34.275682] [] ip_defrag+0x318/0x3fe0 [ 34.281115] [] ? debug_check_no_locks_freed+0x210/0x210 [ 34.288109] [] ? memcpy+0x45/0x50 [ 34.293184] [] ? ip_expire+0x770/0x770 [ 34.298695] [] ip_check_defrag+0x3c8/0x7e0 [ 34.304561] [] ? ip_defrag+0x3fe0/0x3fe0 [ 34.310249] [] packet_rcv_fanout+0x52a/0x5e0 [ 34.316282] [] ? packet_bind+0x190/0x190 [ 34.321974] [] dev_hard_start_xmit+0x644/0x11c0 [ 34.328278] [] ? dev_hard_start_xmit+0xa8/0x11c0 [ 34.334666] [] sch_direct_xmit+0x2c1/0x6e0 [ 34.340525] [] ? dev_watchdog+0x7f0/0x7f0 [ 34.346303] [] __dev_queue_xmit+0xef3/0x1c80 [ 34.352347] [] ? __dev_queue_xmit+0x1d7/0x1c80 [ 34.358582] [] ? debug_check_no_locks_freed+0x210/0x210 [ 34.365575] [] ? netdev_pick_tx+0x2c0/0x2c0 [ 34.371520] [] ? memcpy+0x45/0x50 [ 34.376595] [] dev_queue_xmit+0x17/0x20 [ 34.382209] [] neigh_resolve_output+0x637/0x790 [ 34.388510] [] ? ip_finish_output2+0x6ab/0x1110 [ 34.394810] [] ip_finish_output2+0x6ab/0x1110 [ 34.400930] [] ? ip_finish_output2+0x212/0x1110 [ 34.407223] [] ? nf_ct_deliver_cached_events+0x335/0x560 [ 34.414292] [] ? nf_ct_deliver_cached_events+0x83/0x560 [ 34.421277] [] ? ip_copy_metadata+0x700/0x700 [ 34.427394] [] ? ip_options_fragment+0x1ac/0x280 [ 34.433770] [] ip_do_fragment+0x19cc/0x2190 [ 34.439712] [] ? ip_copy_metadata+0x700/0x700 [ 34.445836] [] ip_fragment.constprop.51+0x143/0x200 [ 34.452473] [] ip_finish_output+0x48a/0xc00 [ 34.458424] [] ip_mc_output+0x233/0x980 [ 34.464019] [] ? ip_queue_xmit+0x1af0/0x1af0 [ 34.470048] [] ? ip_make_skb+0x116/0x210 [ 34.475734] [] ? ip_fragment.constprop.51+0x200/0x200 [ 34.482545] [] ? ip_flush_pending_frames+0x30/0x30 [ 34.489096] [] ip_local_out+0x9b/0x180 [ 34.494605] [] ip_send_skb+0x3c/0xc0 [ 34.499951] [] udp_send_skb+0x5c3/0xc60 [ 34.505548] [] udp_sendmsg+0x16c9/0x1c70 [ 34.511239] [] ? ip_reply_glue_bits+0xc0/0xc0 [ 34.517358] [] ? udp4_lib_lookup+0x60/0x60 [ 34.523217] [] ? debug_check_no_locks_freed+0x210/0x210 [ 34.530214] [] ? sock_has_perm+0x1c1/0x400 [ 34.536072] [] ? sock_has_perm+0x29f/0x400 [ 34.541928] [] ? sock_has_perm+0x9f/0x400 [ 34.547708] [] ? inet_sendmsg+0x143/0x4d0 [ 34.553492] [] inet_sendmsg+0x203/0x4d0 [ 34.559088] [] ? inet_sendmsg+0x73/0x4d0 [ 34.564779] [] ? inet_recvmsg+0x4c0/0x4c0 [ 34.570551] [] sock_sendmsg+0xcc/0x110 [ 34.576071] [] SYSC_sendto+0x21c/0x370 [ 34.581583] [] ? SYSC_connect+0x300/0x300 [ 34.587357] [] ? native_set_pte_at+0xe0/0xe0 [ 34.593389] [] ? do_huge_pmd_anonymous_page+0x737/0x9d0 [ 34.600377] [] ? _raw_spin_unlock+0x2c/0x50 [ 34.606323] [] ? compat_SyS_futex+0x1e1/0x2f0 [ 34.612451] [