[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 21.152874] 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: [ 22.543048] random: sshd: uninitialized urandom read (32 bytes read, 34 bits of entropy available) [ 22.804642] random: sshd: uninitialized urandom read (32 bytes read, 34 bits of entropy available) [ 23.869136] random: nonblocking pool is initialized Warning: Permanently added '10.128.0.51' (ECDSA) to the list of known hosts. net.ipv6.conf.syz_tun.accept_dad = 0 [ 29.779445] IPVS: Creating netns size=2552 id=1 net.ipv6.conf.syz_tun.router_solicitations = 0 executing program [ 29.883167] [ 29.884824] ====================================================== [ 29.891125] [ INFO: possible circular locking dependency detected ] [ 29.897506] 4.4.134-gcb3afe1 #53 Not tainted [ 29.901894] ------------------------------------------------------- [ 29.908283] syz-executor144/3656 is trying to acquire lock: [ 29.913972] (&(&q->lock)->rlock){+.-...}, at: [] ip_defrag+0x318/0x3fe0 [ 29.922836] [ 29.922836] but task is already holding lock: [ 29.928778] (_xmit_NETROM){+.-...}, at: [] sch_direct_xmit+0x23c/0x6e0 [ 29.937572] [ 29.937572] which lock already depends on the new lock. [ 29.937572] [ 29.945863] [ 29.945863] the existing dependency chain (in reverse order) is: [ 29.953457] -> #1 (_xmit_NETROM){+.-...}: [ 29.958222] [] lock_acquire+0x15e/0x450 [ 29.964464] [] _raw_spin_lock_irqsave+0x4e/0x70 [ 29.971397] [] depot_save_stack+0x211/0x610 [ 29.977989] [] save_stack+0xa9/0xd0 [ 29.983882] [] kasan_kmalloc+0xc7/0xe0 [ 29.990038] [] kasan_slab_alloc+0x12/0x20 [ 29.996453] [] kmem_cache_alloc+0xbe/0x2a0 [ 30.002956] [] inet_getpeer.part.5+0xeac/0x15a0 [ 30.009910] [] inet_getpeer+0x55b/0x6f0 [ 30.016158] [] icmp6_send+0x17c5/0x1b80 [ 30.022423] [] icmpv6_param_prob+0x29/0x40 [ 30.028932] [] ipv6_frag_rcv+0x3f94/0x4fd0 [ 30.035437] [] ip6_input_finish+0x32e/0x1550 [ 30.042115] [] ip6_input+0xf6/0x200 [ 30.048008] [] ip6_rcv_finish+0x13d/0x640 [ 30.054430] [] ipv6_rcv+0x10cb/0x1cd0 [ 30.060506] [] __netif_receive_skb_core+0x12d6/0x2940 [ 30.067969] [] __netif_receive_skb+0x5b/0x1b0 [ 30.074738] [] process_backlog+0x216/0x6a0 [ 30.081248] [] net_rx_action+0x3a2/0xdb0 [ 30.087578] [] __do_softirq+0x22c/0xa1a [ 30.093820] [] do_softirq_own_stack+0x1c/0x30 [ 30.100588] [] do_softirq.part.16+0x54/0x60 [ 30.107179] [] do_softirq+0x19/0x20 [ 30.113074] [] netif_rx_ni+0xec/0x3a0 [ 30.119143] [] tun_get_user+0xbe7/0x2410 [ 30.125478] [] tun_chr_write_iter+0xd5/0x190 [ 30.132182] [] do_iter_readv_writev+0x13c/0x1e0 [ 30.139122] [] do_readv_writev+0x2e0/0x6e0 [ 30.145635] [] vfs_writev+0x7b/0xb0 [ 30.151537] [] SyS_writev+0xd9/0x250 [ 30.157522] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 30.164719] -> #0 (&(&q->lock)->rlock){+.-...}: [ 30.170011] [] __lock_acquire+0x3902/0x5270 [ 30.176615] [] lock_acquire+0x15e/0x450 [ 30.182853] [] _raw_spin_lock+0x36/0x50 [ 30.189091] [] ip_defrag+0x318/0x3fe0 [ 30.195165] [] ip_check_defrag+0x3c8/0x7e0 [ 30.201665] [] packet_rcv_fanout+0x52a/0x5e0 [ 30.208341] [] dev_hard_start_xmit+0x644/0x11c0 [ 30.215280] [] sch_direct_xmit+0x2c1/0x6e0 [ 30.221785] [] __dev_queue_xmit+0xef3/0x1c80 [ 30.228459] [] dev_queue_xmit+0x17/0x20 [ 30.234706] [] neigh_resolve_output+0x637/0x790 [ 30.241658] [] ip_finish_output2+0x6ab/0x1110 [ 30.248419] [] ip_do_fragment+0x19cc/0x2190 [ 30.255008] [] ip_fragment.constprop.51+0x143/0x200 [ 30.262290] [] ip_finish_output+0x48a/0xc00 [ 30.268882] [] ip_mc_output+0x233/0x980 [ 30.275124] [] ip_local_out+0x9b/0x180 [ 30.281277] [] ip_send_skb+0x3c/0xc0 [ 30.287258] [] udp_send_skb+0x5c3/0xc60 [ 30.293496] [] udp_sendmsg+0x16c9/0x1c70 [ 30.299825] [] inet_sendmsg+0x203/0x4d0 [ 30.306069] [] sock_sendmsg+0xcc/0x110 [ 30.312235] [] SYSC_sendto+0x21c/0x370 [ 30.318389] [] SyS_sendto+0x40/0x50 [ 30.324296] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 30.331496] [ 30.331496] other info that might help us debug this: [ 30.331496] [ 30.339617] Possible unsafe locking scenario: [ 30.339617] [ 30.345646] CPU0 CPU1 [ 30.350285] ---- ---- [ 30.354924] lock(_xmit_NETROM); [ 30.358587] lock(&(&q->lock)->rlock); [ 30.365292] lock(_xmit_NETROM); [ 30.371482] lock(&(&q->lock)->rlock); [ 30.375673] [ 30.375673] *** DEADLOCK *** [ 30.375673] [ 30.381728] 4 locks held by syz-executor144/3656: [ 30.386548] #0: (rcu_read_lock_bh){......}, at: [] ip_finish_output2+0x212/0x1110 [ 30.396530] #1: (rcu_read_lock_bh){......}, at: [] __dev_queue_xmit+0x1d7/0x1c80 [ 30.406401] #2: (_xmit_NETROM){+.-...}, at: [] sch_direct_xmit+0x23c/0x6e0 [ 30.415742] #3: (rcu_read_lock){......}, at: [] dev_hard_start_xmit+0xa8/0x11c0 [ 30.425503] [ 30.425503] stack backtrace: [ 30.429982] CPU: 1 PID: 3656 Comm: syz-executor144 Not tainted 4.4.134-gcb3afe1 #53 [ 30.437746] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 30.447079] 0000000000000000 0b39ec9710287bf1 ffff8801cf436d38 ffffffff81e0f02d [ 30.455069] ffffffff853eb060 ffffffff853eb720 ffffffff853eb060 ffff8800b31ba150 [ 30.463049] ffff8800b31b9800 ffff8801cf436d80 ffffffff8140e62b 0000000000000003 [ 30.471034] Call Trace: [ 30.473604] [] dump_stack+0xc1/0x124 [ 30.478948] [] print_circular_bug.cold.50+0x1bd/0x27d [ 30.485769] [] __lock_acquire+0x3902/0x5270 [ 30.491718] [] ? debug_check_no_locks_freed+0x210/0x210 [ 30.498706] [] ? trace_hardirqs_on_caller+0x266/0x590 [ 30.505521] [] lock_acquire+0x15e/0x450 [ 30.511125] [] ? ip_defrag+0x318/0x3fe0 [ 30.516725] [] ? inet_frag_find+0x22e/0x9c0 [ 30.522672] [] _raw_spin_lock+0x36/0x50 [ 30.528272] [] ? ip_defrag+0x318/0x3fe0 [ 30.533873] [] ip_defrag+0x318/0x3fe0 [ 30.539305] [] ? debug_check_no_locks_freed+0x210/0x210 [ 30.546296] [] ? memcpy+0x45/0x50 [ 30.551378] [] ? ip_expire+0x770/0x770 [ 30.556894] [] ip_check_defrag+0x3c8/0x7e0 [ 30.562756] [] ? ip_defrag+0x3fe0/0x3fe0 [ 30.568446] [] packet_rcv_fanout+0x52a/0x5e0 [ 30.574485] [] ? packet_bind+0x190/0x190 [ 30.580861] [] dev_hard_start_xmit+0x644/0x11c0 [ 30.587156] [] ? dev_hard_start_xmit+0xa8/0x11c0 [ 30.593540] [] sch_direct_xmit+0x2c1/0x6e0 [ 30.599400] [] ? dev_watchdog+0x7f0/0x7f0 [ 30.605174] [] __dev_queue_xmit+0xef3/0x1c80 [ 30.611208] [] ? __dev_queue_xmit+0x1d7/0x1c80 [ 30.617420] [] ? debug_check_no_locks_freed+0x210/0x210 [ 30.624412] [] ? netdev_pick_tx+0x2c0/0x2c0 [ 30.630364] [] ? memcpy+0x45/0x50 [ 30.635446] [] dev_queue_xmit+0x17/0x20 [ 30.641045] [] neigh_resolve_output+0x637/0x790 [ 30.647339] [] ? ip_finish_output2+0x6ab/0x1110 [ 30.653634] [] ip_finish_output2+0x6ab/0x1110 [ 30.659756] [] ? ip_finish_output2+0x212/0x1110 [ 30.666064] [] ? nf_ct_deliver_cached_events+0x335/0x560 [ 30.673141] [] ? ip_copy_metadata+0x700/0x700 [ 30.679266] [] ip_do_fragment+0x19cc/0x2190 [ 30.685225] [] ? ip_copy_metadata+0x700/0x700 [ 30.691350] [] ip_fragment.constprop.51+0x143/0x200 [ 30.697995] [] ip_finish_output+0x48a/0xc00 [ 30.703943] [] ip_mc_output+0x233/0x980 [ 30.709547] [] ? ip_queue_xmit+0x1af0/0x1af0 [ 30.715590] [] ? ip_make_skb+0x116/0x210 [ 30.721287] [] ? ip_fragment.constprop.51+0x200/0x200 [ 30.728108] [] ? ip_flush_pending_frames+0x30/0x30 [ 30.734667] [] ip_local_out+0x9b/0x180 [ 30.740191] [] ip_send_skb+0x3c/0xc0 [ 30.745533] [] udp_send_skb+0x5c3/0xc60 [ 30.751135] [] udp_sendmsg+0x16c9/0x1c70 [ 30.756822] [] ? ip_reply_glue_bits+0xc0/0xc0 [ 30.762942] [] ? udp4_lib_lookup+0x60/0x60 [ 30.768804] [] ? debug_check_no_locks_freed+0x210/0x210 [ 30.775795] [] ? sock_has_perm+0x1c1/0x400 [ 30.781663] [] ? sock_has_perm+0x29f/0x400 [ 30.787520] [] ? sock_has_perm+0x9f/0x400 [ 30.793297] [] ? inet_sendmsg+0x143/0x4d0 [ 30.799072] [] inet_sendmsg+0x203/0x4d0 [ 30.804671] [] ? inet_sendmsg+0x73/0x4d0 [ 30.810357] [] ? inet_recvmsg+0x4c0/0x4c0 [ 30.816143] [] sock_sendmsg+0xcc/0x110 [ 30.821656] [] SYSC_sendto+0x21c/0x370 [ 30.827173] [] ? SYSC_connect+0x300/0x300 [ 30.832945] [] ? _raw_spin_unlock+0x2c/0x50 [ 30.838898] [] ? do_huge_pmd_anonymous_page+0x38c/0x9d0 [ 30.845890] [] ? handle_mm_fault+0xbf7/0x30b0 [ 30.852015] [] ? SYSC_connect+0x22a/0x300 [ 30.857796] [] ? __do_page_fault+0x385/0xa10 [ 30.863838] [] ? retint_user+0x18/0x3c [ 30.869355] [] SyS_sendto+0x40/0x50 [ 30.874611] [] entry_SYSCALL_64_fastpath+0x22/0x9e