[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Starting mcstransd: [ 11.467185] random: sshd: uninitialized urandom read (32 bytes read) [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting file context maintaining daemon: restorecond[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [ 12.464199] random: crng init done Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.33' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 35.090433] netlink: 8 bytes leftover after parsing attributes in process `syz-executor580'. [ 35.126263] [ 35.127898] =============================== [ 35.132190] [ INFO: suspicious RCU usage. ] [ 35.136520] 4.9.155+ #27 Not tainted [ 35.140209] ------------------------------- [ 35.144498] net/ipv6/ip6_fib.c:1470 suspicious rcu_dereference_protected() usage! [ 35.152117] [ 35.152117] other info that might help us debug this: [ 35.152117] [ 35.160248] [ 35.160248] rcu_scheduler_active = 2, debug_locks = 0 [ 35.166923] 4 locks held by syz-executor580/2072: [ 35.171736] #0: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 [ 35.180098] #1: (&(&net->ipv6.fib6_gc_lock)->rlock){+.....}, at: [] fib6_run_gc+0x22c/0x2e0 [ 35.190876] #2: (rcu_read_lock){......}, at: [] __fib6_clean_all+0x0/0x230 [ 35.200111] #3: (&tb->tb6_lock){++....}, at: [] __fib6_clean_all+0xe3/0x230 [ 35.209420] [ 35.209420] stack backtrace: [ 35.213893] CPU: 0 PID: 2072 Comm: syz-executor580 Not tainted 4.9.155+ #27 [ 35.220968] ffff8801ce2d7470 ffffffff81b47871 ffff8801ce8b0380 0000000000000000 [ 35.228941] 0000000000000002 00000000000005be ffff8801d25a5f00 ffff8801ce2d74a0 [ 35.236996] ffffffff813fed99 ffff8801ce2d76c0 dffffc0000000000 00000000ffffffff [ 35.244980] Call Trace: [ 35.247582] [] dump_stack+0xc1/0x120 [ 35.252931] [] lockdep_rcu_suspicious.cold+0x10a/0x149 [ 35.259839] [] fib6_del+0x81f/0xb20 [ 35.265088] [] fib6_clean_node+0x29c/0x4d0 [ 35.270943] [] ? fib6_del+0xb20/0xb20 [ 35.276366] [] ? mark_held_locks+0xb1/0x100 [ 35.282306] [] ? __local_bh_enable_ip+0x6a/0xe0 [ 35.288602] [] ? trace_hardirqs_on_caller+0x260/0x5a0 [ 35.295417] [] ? fib6_walker_link+0xf6/0x140 [ 35.301452] [] fib6_walk_continue+0x3e0/0x630 [ 35.307572] [] fib6_walk+0x9d/0xf0 [ 35.312733] [] ? fib6_flush_trees+0xc0/0xc0 [ 35.318676] [] fib6_clean_tree+0xe7/0x120 [ 35.324451] [] ? fib6_walk+0xf0/0xf0 [ 35.329795] [] ? check_preemption_disabled+0x3c/0x200 [ 35.336611] [] ? fib6_del+0xb20/0xb20 [ 35.342032] [] ? fib6_flush_trees+0xc0/0xc0 [ 35.347981] [] ? check_preemption_disabled+0x3c/0x200 [ 35.354831] [] ? fib6_clean_tree+0x120/0x120 [ 35.360879] [] __fib6_clean_all+0xfb/0x230 [ 35.366733] [] ? fib6_clean_tree+0x120/0x120 [ 35.372763] [] ? fib6_flush_trees+0xc0/0xc0 [ 35.378705] [] fib6_run_gc+0x124/0x2e0 [ 35.384213] [] ? fib6_clean_all+0x30/0x30 [ 35.389984] [] ? neigh_ifdown+0x242/0x2e0 [ 35.395760] [] ndisc_netdev_event+0x2ab/0x350 [ 35.401878] [] notifier_call_chain+0xb4/0x1d0 [ 35.408004] [] raw_notifier_call_chain+0x2e/0x40 [ 35.414385] [] call_netdevice_notifiers_info+0x56/0x70 [ 35.421290] [] dev_close_many+0x2f3/0x6a0 [ 35.427071] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 35.433837] [] ? __dev_close_many+0x270/0x270 [ 35.440102] [] rollback_registered_many+0x3a0/0xb50 [ 35.446751] [] ? free_netdev+0x300/0x300 [ 35.452434] [] ? mark_held_locks+0xb1/0x100 [ 35.458379] [] ? queue_delayed_work_on+0x83/0xb0 [ 35.464758] [] rollback_registered+0xf2/0x1b0 [ 35.470883] [] ? rollback_registered_many+0xb50/0xb50 [ 35.477702] [] ? linkwatch_schedule_work+0xf8/0x130 [ 35.484339] [] unregister_netdevice_queue+0x1ae/0x230 [ 35.491151] [] __tun_detach+0x820/0xa00 [ 35.496744] [] ? __tun_detach+0xa00/0xa00 [ 35.502514] [] tun_chr_close+0x46/0x60 [ 35.508029] [] __fput+0x274/0x720 [ 35.513105] [] ____fput+0x16/0x20 [ 35.518182] [] task_work_run+0x108/0x180 [ 35.523862] [] do_exit+0x78b/0x2aa0 [ 35.529111] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 35.535841] [] ? release_task+0x14a0/0x14a0 [ 35.541787] [] ? __do_page_fault+0x41e/0xa60 [ 35.547866] [] ? up_read+0x1a/0x40 [ 35.553034] [] ? __do_page_fault+0x545/0xa60 [ 35.559107] [] do_group_exit+0x111/0x300 [ 35.564800] [] SyS_exit_group+0x1d/0x20 [ 35.570399] [] ? do_group_exit+0x300/0x300 [ 35.576253] [