[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 19.526840] 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: [ 23.484987] random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available) [ 23.709434] random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available) [ 25.153428] random: sshd: uninitialized urandom read (32 bytes read, 126 bits of entropy available) [ 25.281658] random: nonblocking pool is initialized Warning: Permanently added '10.128.10.16' (ECDSA) to the list of known hosts. 2018/07/22 20:16:04 parsed 1 programs 2018/07/22 20:16:06 executed programs: 0 [ 41.876714] IPVS: Creating netns size=2552 id=1 [ 41.980204] [ 41.981848] ====================================================== [ 41.988137] [ INFO: possible circular locking dependency detected ] [ 41.994514] 4.4.141-g1b37d68 #7 Not tainted [ 41.998803] ------------------------------------------------------- [ 42.005176] syz-executor0/3870 is trying to acquire lock: [ 42.010679] (&(&q->lock)->rlock){+.-...}, at: [] ip_defrag+0x318/0x3fe0 [ 42.019525] [ 42.019525] but task is already holding lock: [ 42.025464] (_xmit_NETROM){+.-...}, at: [] sch_direct_xmit+0x23c/0x6e0 [ 42.034218] [ 42.034218] which lock already depends on the new lock. [ 42.034218] [ 42.042500] [ 42.042500] the existing dependency chain (in reverse order) is: [ 42.050088] -> #1 (_xmit_NETROM){+.-...}: [ 42.054854] [] lock_acquire+0x15e/0x450 [ 42.061098] [] _raw_spin_lock_irqsave+0x4e/0x70 [ 42.068025] [] depot_save_stack+0x211/0x610 [ 42.074608] [] save_stack+0xa9/0xd0 [ 42.080493] [] kasan_kmalloc+0xc7/0xe0 [ 42.086639] [] kasan_slab_alloc+0x12/0x20 [ 42.093043] [] kmem_cache_alloc+0xbe/0x2a0 [ 42.099554] [] inet_getpeer.part.5+0xeac/0x15a0 [ 42.106492] [] inet_getpeer+0x55b/0x6f0 [ 42.112723] [] icmp6_send+0x17c5/0x1b80 [ 42.118964] [] icmpv6_param_prob+0x29/0x40 [ 42.125459] [] ipv6_frag_rcv+0x3f94/0x4fd0 [ 42.131951] [] ip6_input_finish+0x32e/0x1550 [ 42.138621] [] ip6_input+0xf6/0x200 [ 42.144505] [] ip6_rcv_finish+0x13d/0x640 [ 42.150911] [] ipv6_rcv+0x10cb/0x1cd0 [ 42.156970] [] __netif_receive_skb_core+0x12d6/0x2940 [ 42.164422] [] __netif_receive_skb+0x5b/0x1b0 [ 42.171178] [] process_backlog+0x216/0x6a0 [ 42.177762] [] net_rx_action+0x3a2/0xdb0 [ 42.184078] [] __do_softirq+0x22c/0xa1a [ 42.190319] [] do_softirq_own_stack+0x1c/0x30 [ 42.197072] [] do_softirq.part.16+0x54/0x60 [ 42.203652] [] do_softirq+0x19/0x20 [ 42.209534] [] netif_rx_ni+0xec/0x3a0 [ 42.215593] [] tun_get_user+0xbe7/0x2410 [ 42.221911] [] tun_chr_write_iter+0xd5/0x190 [ 42.228578] [] do_iter_readv_writev+0x13c/0x1e0 [ 42.235505] [] compat_do_readv_writev+0x2e2/0x6e0 [ 42.242603] [] compat_writev+0xe1/0x150 [ 42.248834] [] compat_SyS_writev+0xd8/0x1c0 [ 42.255411] [] do_fast_syscall_32+0x326/0x8b0 [ 42.262167] [] sysenter_flags_fixed+0xd/0x17 [ 42.268844] -> #0 (&(&q->lock)->rlock){+.-...}: [ 42.274133] [] __lock_acquire+0x3902/0x5270 [ 42.280714] [] lock_acquire+0x15e/0x450 [ 42.286944] [] _raw_spin_lock+0x36/0x50 [ 42.293183] [] ip_defrag+0x318/0x3fe0 [ 42.299241] [] ip_check_defrag+0x3c8/0x7e0 [ 42.305735] [] packet_rcv_fanout+0x52a/0x5e0 [ 42.312403] [] dev_hard_start_xmit+0x644/0x11c0 [ 42.319330] [] sch_direct_xmit+0x2c1/0x6e0 [ 42.325834] [] __dev_queue_xmit+0xef3/0x1c80 [ 42.332509] [] dev_queue_xmit+0x17/0x20 [ 42.338749] [] neigh_resolve_output+0x637/0x790 [ 42.345680] [] ip_finish_output2+0x6ab/0x1110 [ 42.352454] [] ip_do_fragment+0x19cc/0x2190 [ 42.359037] [] ip_fragment.constprop.51+0x143/0x200 [ 42.366329] [] ip_finish_output+0x48a/0xc00 [ 42.372936] [] ip_mc_output+0x233/0x980 [ 42.379176] [] ip_local_out+0x9b/0x180 [ 42.385318] [] ip_send_skb+0x3c/0xc0 [ 42.391287] [] udp_send_skb+0x5c3/0xc60 [ 42.397522] [] udp_sendmsg+0x16c9/0x1c70 [ 42.403848] [] inet_sendmsg+0x203/0x4d0 [ 42.410080] [] sock_sendmsg+0xcc/0x110 [ 42.416236] [] SYSC_sendto+0x21c/0x370 [ 42.422399] [] SyS_sendto+0x40/0x50 [ 42.428301] [] do_fast_syscall_32+0x326/0x8b0 [ 42.435054] [] sysenter_flags_fixed+0xd/0x17 [ 42.441721] [ 42.441721] other info that might help us debug this: [ 42.441721] [ 42.449833] Possible unsafe locking scenario: [ 42.449833] [ 42.455858] CPU0 CPU1 [ 42.460492] ---- ---- [ 42.465129] lock(_xmit_NETROM); [ 42.468799] lock(&(&q->lock)->rlock); [ 42.475508] lock(_xmit_NETROM); [ 42.481896] lock(&(&q->lock)->rlock); [ 42.486071] [ 42.486071] *** DEADLOCK *** [ 42.486071] [ 42.492101] 4 locks held by syz-executor0/3870: [ 42.496738] #0: (rcu_read_lock_bh){......}, at: [] ip_finish_output2+0x212/0x1110 [ 42.506662] #1: (rcu_read_lock_bh){......}, at: [] __dev_queue_xmit+0x1d7/0x1c80 [ 42.516529] #2: (_xmit_NETROM){+.-...}, at: [] sch_direct_xmit+0x23c/0x6e0 [ 42.525852] #3: (rcu_read_lock){......}, at: [] dev_hard_start_xmit+0xa8/0x11c0 [ 42.535633] [ 42.535633] stack backtrace: [ 42.540106] CPU: 1 PID: 3870 Comm: syz-executor0 Not tainted 4.4.141-g1b37d68 #7 [ 42.547607] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 42.556928] 0000000000000000 cdbb15f4c1c3e5eb ffff8800bad1ecc8 ffffffff81e0e18d [ 42.564937] ffffffff853ed3d0 ffffffff853ecd10 ffffffff853ed3d0 ffff8800bad80950 [ 42.572968] ffff8800bad80000 ffff8800bad1ed10 ffffffff8140e71b 0000000000000003 [ 42.580961] Call Trace: [ 42.583518] [] dump_stack+0xc1/0x124 [ 42.588853] [] print_circular_bug.cold.50+0x1bd/0x27d [ 42.595663] [] __lock_acquire+0x3902/0x5270 [ 42.601620] [] ? debug_check_no_locks_freed+0x210/0x210 [ 42.608611] [] ? trace_hardirqs_on_caller+0x266/0x590 [ 42.615445] [] lock_acquire+0x15e/0x450 [ 42.621046] [] ? ip_defrag+0x318/0x3fe0 [ 42.626640] [] ? inet_frag_find+0x22e/0x9c0 [ 42.632581] [] _raw_spin_lock+0x36/0x50 [ 42.638180] [] ? ip_defrag+0x318/0x3fe0 [ 42.643778] [] ip_defrag+0x318/0x3fe0 [ 42.649199] [] ? debug_check_no_locks_freed+0x210/0x210 [ 42.656189] [] ? memcpy+0x45/0x50 [ 42.661262] [] ? ip_expire+0x770/0x770 [ 42.666776] [] ip_check_defrag+0x3c8/0x7e0 [ 42.672637] [] ? ip_defrag+0x3fe0/0x3fe0 [ 42.678316] [] packet_rcv_fanout+0x52a/0x5e0 [ 42.684344] [] ? packet_bind+0x190/0x190 [ 42.690033] [] dev_hard_start_xmit+0x644/0x11c0 [ 42.696319] [] ? dev_hard_start_xmit+0xa8/0x11c0 [ 42.702701] [] sch_direct_xmit+0x2c1/0x6e0 [ 42.708562] [] ? dev_watchdog+0x7f0/0x7f0 [ 42.714336] [] __dev_queue_xmit+0xef3/0x1c80 [ 42.720371] [] ? __dev_queue_xmit+0x1d7/0x1c80 [ 42.726575] [] ? debug_check_no_locks_freed+0x210/0x210 [ 42.733582] [] ? netdev_pick_tx+0x2c0/0x2c0 [ 42.739528] [] ? memcpy+0x45/0x50 [ 42.744602] [] dev_queue_xmit+0x17/0x20 [ 42.750194] [] neigh_resolve_output+0x637/0x790 [ 42.756483] [] ? ip_finish_output2+0x6ab/0x1110 [ 42.762768] [] ip_finish_output2+0x6ab/0x1110 [ 42.768881] [] ? ip_finish_output2+0x212/0x1110 [ 42.775167] [] ? nf_ct_deliver_cached_events+0x335/0x560 [ 42.782235] [] ? nf_ct_deliver_cached_events+0x83/0x560 [ 42.789214] [] ? ip_copy_metadata+0x700/0x700 [ 42.795326] [] ? ip_options_fragment+0x1ac/0x280 [ 42.801700] [] ip_do_fragment+0x19cc/0x2190 [ 42.807638] [] ? ip_copy_metadata+0x700/0x700 [ 42.813751] [] ip_fragment.constprop.51+0x143/0x200 [ 42.820384] [] ip_finish_output+0x48a/0xc00 [ 42.826321] [] ip_mc_output+0x233/0x980 [ 42.831911] [] ? ip_queue_xmit+0x1af0/0x1af0 [ 42.837939] [] ? ip_make_skb+0x116/0x210 [ 42.843618] [] ? ip_fragment.constprop.51+0x200/0x200 [ 42.850424] [] ? ip_flush_pending_frames+0x30/0x30 [ 42.856968] [] ip_local_out+0x9b/0x180 [ 42.862471] [] ip_send_skb+0x3c/0xc0 [ 42.867803] [] udp_send_skb+0x5c3/0xc60 [ 42.873393] [] udp_sendmsg+0x16c9/0x1c70 [ 42.879070] [] ? ip_reply_glue_bits+0xc0/0xc0 [ 42.885182] [] ? udp4_lib_lookup+0x60/0x60 [ 42.891038] [] ? debug_check_no_locks_freed+0x210/0x210 [ 42.898029] [] ? sock_has_perm+0x1c1/0x400 [ 42.903880] [] ? sock_has_perm+0x29f/0x400 [ 42.909731] [] ? sock_has_perm+0x9f/0x400 [ 42.915499] [] ? inet_sendmsg+0x143/0x4d0 [ 42.921267] [] inet_sendmsg+0x203/0x4d0 [ 42.926857] [] ? inet_sendmsg+0x73/0x4d0 [ 42.932534] [] ? inet_recvmsg+0x4c0/0x4c0 [ 42.938298] [] sock_sendmsg+0xcc/0x110 [ 42.943802] [] SYSC_sendto+0x21c/0x370 [ 42.949307] [] ? SYSC_connect+0x300/0x300 [ 42.955074] [] ? native_set_pte_at+0xe0/0xe0 [ 42.961104] [] ? do_huge_pmd_anonymous_page+0x737/0x9d0 [ 42.968085] [] ? _raw_spin_unlock+0x2c/0x50 [ 42.974028] [] ? compat_SyS_futex+0x1e1/0x2f0 [ 42.980144] [] ? compat_SyS_get_robust_list+0x310/0x310 [ 42.987125] [] SyS_sendto+0x40/0x50 [ 42.992371] [] ? SyS_getpeername+0x30/0x30 [ 42.998226] [] do_fast_syscall_32+0x326/0x8b0 [ 43.004338] [] sysenter_flags_fixed+0xd/0x17