[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 19.976051] 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: [ 22.124606] random: sshd: uninitialized urandom read (32 bytes read, 35 bits of entropy available) [ 22.351523] random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available) [ 23.774054] random: sshd: uninitialized urandom read (32 bytes read, 107 bits of entropy available) [ 23.924250] random: sshd: uninitialized urandom read (32 bytes read, 110 bits of entropy available) Warning: Permanently added '10.128.0.7' (ECDSA) to the list of known hosts. [ 29.388616] random: sshd: uninitialized urandom read (32 bytes read, 114 bits of entropy available) 2018/07/14 07:29:49 parsed 1 programs [ 30.892094] random: cc1: uninitialized urandom read (8 bytes read, 116 bits of entropy available) 2018/07/14 07:29:52 executed programs: 0 [ 32.207757] IPVS: Creating netns size=2552 id=1 [ 32.316389] [ 32.318044] ====================================================== [ 32.324341] [ INFO: possible circular locking dependency detected ] [ 32.330718] 4.4.140-ged9bdc8 #4 Not tainted [ 32.335018] ------------------------------------------------------- [ 32.341394] syz-executor0/3882 is trying to acquire lock: [ 32.346910] (&(&q->lock)->rlock){+.-...}, at: [] ip_defrag+0x318/0x3fe0 [ 32.355783] [ 32.355783] but task is already holding lock: [ 32.361986] (_xmit_NETROM){+.-...}, at: [] sch_direct_xmit+0x23c/0x6e0 [ 32.370759] [ 32.370759] which lock already depends on the new lock. [ 32.370759] [ 32.379047] [ 32.379047] the existing dependency chain (in reverse order) is: [ 32.387420] -> #1 (_xmit_NETROM){+.-...}: [ 32.392186] [] lock_acquire+0x15e/0x450 [ 32.398436] [] _raw_spin_lock_irqsave+0x4e/0x70 [ 32.405372] [] depot_save_stack+0x211/0x610 [ 32.411961] [] save_stack+0xa9/0xd0 [ 32.417854] [] kasan_kmalloc+0xc7/0xe0 [ 32.424007] [] kasan_slab_alloc+0x12/0x20 [ 32.430435] [] kmem_cache_alloc+0xbe/0x2a0 [ 32.436942] [] inet_getpeer.part.5+0xeac/0x15a0 [ 32.444490] [] inet_getpeer+0x55b/0x6f0 [ 32.450726] [] icmp6_send+0x17c5/0x1b80 [ 32.456962] [] icmpv6_param_prob+0x29/0x40 [ 32.463474] [] ipv6_frag_rcv+0x3f94/0x4fd0 [ 32.469977] [] ip6_input_finish+0x32e/0x1550 [ 32.476649] [] ip6_input+0xf6/0x200 [ 32.482538] [] ip6_rcv_finish+0x13d/0x640 [ 32.488951] [] ipv6_rcv+0x10cb/0x1cd0 [ 32.495014] [] __netif_receive_skb_core+0x12d6/0x2940 [ 32.502469] [] __netif_receive_skb+0x5b/0x1b0 [ 32.509228] [] process_backlog+0x216/0x6a0 [ 32.515730] [] net_rx_action+0x3a2/0xdb0 [ 32.522053] [] __do_softirq+0x22c/0xa1a [ 32.528289] [] do_softirq_own_stack+0x1c/0x30 [ 32.535046] [] do_softirq.part.16+0x54/0x60 [ 32.541646] [] do_softirq+0x19/0x20 [ 32.547536] [] netif_rx_ni+0xec/0x3a0 [ 32.553601] [] tun_get_user+0xbe7/0x2410 [ 32.559938] [] tun_chr_write_iter+0xd5/0x190 [ 32.566605] [] do_iter_readv_writev+0x13c/0x1e0 [ 32.573619] [] compat_do_readv_writev+0x2e2/0x6e0 [ 32.580723] [] compat_writev+0xe1/0x150 [ 32.586964] [] compat_SyS_writev+0xd8/0x1c0 [ 32.593557] [] do_fast_syscall_32+0x326/0x8b0 [ 32.600317] [] sysenter_flags_fixed+0xd/0x17 [ 32.606990] -> #0 (&(&q->lock)->rlock){+.-...}: [ 32.612284] [] __lock_acquire+0x3902/0x5270 [ 32.618867] [] lock_acquire+0x15e/0x450 [ 32.625107] [] _raw_spin_lock+0x36/0x50 [ 32.631342] [] ip_defrag+0x318/0x3fe0 [ 32.637410] [] ip_check_defrag+0x3c8/0x7e0 [ 32.643910] [] packet_rcv_fanout+0x52a/0x5e0 [ 32.650583] [] dev_hard_start_xmit+0x644/0x11c0 [ 32.657521] [] sch_direct_xmit+0x2c1/0x6e0 [ 32.664016] [] __dev_queue_xmit+0xef3/0x1c80 [ 32.670683] [] dev_queue_xmit+0x17/0x20 [ 32.676924] [] neigh_resolve_output+0x637/0x790 [ 32.683856] [] ip_finish_output2+0x6ab/0x1110 [ 32.690612] [] ip_do_fragment+0x19cc/0x2190 [ 32.697202] [] ip_fragment.constprop.51+0x143/0x200 [ 32.704487] [] ip_finish_output+0x48a/0xc00 [ 32.711080] [] ip_mc_output+0x233/0x980 [ 32.717315] [] ip_local_out+0x9b/0x180 [ 32.723464] [] ip_send_skb+0x3c/0xc0 [ 32.729439] [] udp_send_skb+0x5c3/0xc60 [ 32.735687] [] udp_sendmsg+0x16c9/0x1c70 [ 32.742016] [] inet_sendmsg+0x203/0x4d0 [ 32.748253] [] sock_sendmsg+0xcc/0x110 [ 32.754410] [] SYSC_sendto+0x21c/0x370 [ 32.760561] [] SyS_sendto+0x40/0x50 [ 32.766459] [] do_fast_syscall_32+0x326/0x8b0 [ 32.773214] [] sysenter_flags_fixed+0xd/0x17 [ 32.779880] [ 32.779880] other info that might help us debug this: [ 32.779880] [ 32.788001] Possible unsafe locking scenario: [ 32.788001] [ 32.794036] CPU0 CPU1 [ 32.798673] ---- ---- [ 32.803310] lock(_xmit_NETROM); [ 32.806970] lock(&(&q->lock)->rlock); [ 32.813681] lock(_xmit_NETROM); [ 32.819854] lock(&(&q->lock)->rlock); [ 32.824034] [ 32.824034] *** DEADLOCK *** [ 32.824034] [ 32.830065] 4 locks held by syz-executor0/3882: [ 32.834703] #0: (rcu_read_lock_bh){......}, at: [] ip_finish_output2+0x212/0x1110 [ 32.844654] #1: (rcu_read_lock_bh){......}, at: [] __dev_queue_xmit+0x1d7/0x1c80 [ 32.854525] #2: (_xmit_NETROM){+.-...}, at: [] sch_direct_xmit+0x23c/0x6e0 [ 32.863854] #3: (rcu_read_lock){......}, at: [] dev_hard_start_xmit+0xa8/0x11c0 [ 32.873612] [ 32.873612] stack backtrace: [ 32.878082] CPU: 1 PID: 3882 Comm: syz-executor0 Not tainted 4.4.140-ged9bdc8 #4 [ 32.885590] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 32.894916] 0000000000000000 b711604059e11f32 ffff8800ba56ecc8 ffffffff81e0e08d [ 32.902902] ffffffff853ebf50 ffffffff853eb890 ffffffff853ebf50 ffff8800bab5a150 [ 32.910883] ffff8800bab59800 ffff8800ba56ed10 ffffffff8140e6eb 0000000000000003 [ 32.918867] Call Trace: [ 32.921428] [] dump_stack+0xc1/0x124 [ 32.926767] [] print_circular_bug.cold.50+0x1bd/0x27d [ 32.933579] [] __lock_acquire+0x3902/0x5270 [ 32.939527] [] ? debug_check_no_locks_freed+0x210/0x210 [ 32.946509] [] ? trace_hardirqs_on_caller+0x266/0x590 [ 32.953320] [] lock_acquire+0x15e/0x450 [ 32.958923] [] ? ip_defrag+0x318/0x3fe0 [ 32.964521] [] ? inet_frag_find+0x22e/0x9c0 [ 32.970466] [] _raw_spin_lock+0x36/0x50 [ 32.976061] [] ? ip_defrag+0x318/0x3fe0 [ 32.981668] [] ip_defrag+0x318/0x3fe0 [ 32.987100] [] ? debug_check_no_locks_freed+0x210/0x210 [ 32.994092] [] ? memcpy+0x45/0x50 [ 32.999171] [] ? ip_expire+0x770/0x770 [ 33.004683] [] ip_check_defrag+0x3c8/0x7e0 [ 33.010548] [] ? ip_defrag+0x3fe0/0x3fe0 [ 33.016229] [] packet_rcv_fanout+0x52a/0x5e0 [ 33.022267] [] ? packet_bind+0x190/0x190 [ 33.028037] [] dev_hard_start_xmit+0x644/0x11c0 [ 33.034328] [] ? dev_hard_start_xmit+0xa8/0x11c0 [ 33.040704] [] sch_direct_xmit+0x2c1/0x6e0 [ 33.046579] [] ? dev_watchdog+0x7f0/0x7f0 [ 33.052401] [] __dev_queue_xmit+0xef3/0x1c80 [ 33.058444] [] ? __dev_queue_xmit+0x1d7/0x1c80 [ 33.064651] [] ? debug_check_no_locks_freed+0x210/0x210 [ 33.071640] [] ? netdev_pick_tx+0x2c0/0x2c0 [ 33.077590] [] ? memcpy+0x45/0x50 [ 33.082665] [] dev_queue_xmit+0x17/0x20 [ 33.088260] [] neigh_resolve_output+0x637/0x790 [ 33.094561] [] ? ip_finish_output2+0x6ab/0x1110 [ 33.100859] [] ip_finish_output2+0x6ab/0x1110 [ 33.106978] [] ? ip_finish_output2+0x212/0x1110 [ 33.113272] [] ? nf_ct_deliver_cached_events+0x335/0x560 [ 33.120785] [] ? nf_ct_deliver_cached_events+0x83/0x560 [ 33.127778] [] ? ip_copy_metadata+0x700/0x700 [ 33.133900] [] ? ip_options_fragment+0x1ac/0x280 [ 33.140279] [] ip_do_fragment+0x19cc/0x2190 [ 33.146224] [] ? ip_copy_metadata+0x700/0x700 [ 33.152347] [] ip_fragment.constprop.51+0x143/0x200 [ 33.158992] [] ip_finish_output+0x48a/0xc00 [ 33.164954] [] ip_mc_output+0x233/0x980 [ 33.170558] [] ? ip_queue_xmit+0x1af0/0x1af0 [ 33.176590] [] ? ip_make_skb+0x116/0x210 [ 33.182272] [] ? ip_fragment.constprop.51+0x200/0x200 [ 33.189085] [] ? ip_flush_pending_frames+0x30/0x30 [ 33.195635] [] ip_local_out+0x9b/0x180 [ 33.201145] [] ip_send_skb+0x3c/0xc0 [ 33.206568] [] udp_send_skb+0x5c3/0xc60 [ 33.212164] [] udp_sendmsg+0x16c9/0x1c70 [ 33.217846] [] ? ip_reply_glue_bits+0xc0/0xc0 [ 33.223971] [] ? udp4_lib_lookup+0x60/0x60 [ 33.229833] [] ? debug_check_no_locks_freed+0x210/0x210 [ 33.236817] [] ? sock_has_perm+0x1c1/0x400 [ 33.242673] [] ? sock_has_perm+0x29f/0x400 [ 33.248540] [] ? sock_has_perm+0x9f/0x400 [ 33.254323] [] ? inet_sendmsg+0x143/0x4d0 [ 33.260102] [] inet_sendmsg+0x203/0x4d0 [ 33.265709] [] ? inet_sendmsg+0x73/0x4d0 [ 33.271399] [] ? inet_recvmsg+0x4c0/0x4c0 [ 33.277179] [] sock_sendmsg+0xcc/0x110 [ 33.282696] [] SYSC_sendto+0x21c/0x370 [ 33.288211] [] ? SYSC_connect+0x300/0x300 [ 33.293987] [] ? native_set_pte_at+0xe0/0xe0 [ 33.300019] [] ? do_huge_pmd_anonymous_page+0x737/0x9d0 [ 33.307004] [] ? _raw_spin_unlock+0x2c/0x50 [ 33.312949] [] ? compat_SyS_futex+0x1e1/0x2f0 [ 33.319074] [