[ OK ] Reached target Graphical Interface. Starting Update UTMP about System Runlevel Changes... Starting Load/Save RF Kill Switch Status... [ OK ] Started Update UTMP about System Runlevel Changes. [ OK ] Started Load/Save RF Kill Switch Status. Debian GNU/Linux 9 syzkaller ttyS0 Warning: Permanently added '10.128.1.26' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 29.706018] [ 29.707960] ============================= [ 29.713128] WARNING: suspicious RCU usage [ 29.717266] 4.14.209-syzkaller #0 Not tainted [ 29.723046] ----------------------------- [ 29.727187] net/tipc/bearer.c:177 suspicious rcu_dereference_protected() usage! [ 29.735320] [ 29.735320] other info that might help us debug this: [ 29.735320] [ 29.744053] [ 29.744053] rcu_scheduler_active = 2, debug_locks = 1 [ 29.751562] 2 locks held by syz-executor171/8018: [ 29.756408] #0: (cb_lock){++++}, at: [] genl_rcv+0x15/0x40 [ 29.764618] #1: (genl_mutex){+.+.}, at: [] genl_rcv_msg+0x112/0x140 [ 29.773307] [ 29.773307] stack backtrace: [ 29.778370] CPU: 1 PID: 8018 Comm: syz-executor171 Not tainted 4.14.209-syzkaller #0 [ 29.786236] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 29.795572] Call Trace: [ 29.798164] dump_stack+0x1b2/0x283 [ 29.801793] tipc_bearer_find+0x1ff/0x2f0 [ 29.805937] tipc_nl_compat_link_set+0x40b/0xb90 [ 29.810677] ? __alloc_skb+0x3dc/0x510 [ 29.814555] tipc_nl_compat_doit+0x192/0x5d0 [ 29.818964] ? tipc_nl_compat_link_set+0xb90/0xb90 [ 29.823890] ? security_capable+0x88/0xb0 [ 29.828022] ? ns_capable_common+0x127/0x150 [ 29.832418] tipc_nl_compat_recv+0xa0b/0xae0 [ 29.836814] ? tipc_nl_compat_dumpit+0x7a0/0x7a0 [ 29.841554] ? tipc_nl_node_dump+0xc20/0xc20 [ 29.845974] ? __tipc_add_link_prop.isra.0+0x190/0x190 [ 29.851265] ? lock_downgrade+0x740/0x740 [ 29.855465] genl_family_rcv_msg+0x572/0xb20 [ 29.859864] ? __lock_acquire+0x5fc/0x3f20 [ 29.864083] ? genl_rcv+0x40/0x40 [ 29.867541] ? __ww_mutex_wakeup_for_backoff+0x210/0x210 [ 29.872974] ? trace_hardirqs_on+0x10/0x10 [ 29.877212] ? sock_sendmsg+0xb5/0x100 [ 29.881093] genl_rcv_msg+0xaf/0x140 [ 29.884803] netlink_rcv_skb+0x125/0x390 [ 29.888858] ? genl_family_rcv_msg+0xb20/0xb20 [ 29.893418] ? netlink_ack+0x9a0/0x9a0 [ 29.897298] ? lock_acquire+0x170/0x3f0 [ 29.901268] genl_rcv+0x24/0x40 [ 29.904538] netlink_unicast+0x437/0x610 [ 29.908579] ? netlink_sendskb+0xd0/0xd0 [ 29.912638] ? __check_object_size+0x179/0x22c [ 29.917213] netlink_sendmsg+0x62e/0xb80 [ 29.921297] ? nlmsg_notify+0x170/0x170 [ 29.925260] ? kernel_recvmsg+0x210/0x210 [ 29.929440] ? security_socket_sendmsg+0x83/0xb0 [ 29.934188] ? nlmsg_notify+0x170/0x170 [ 29.938152] sock_sendmsg+0xb5/0x100 [ 29.941868] ___sys_sendmsg+0x6c8/0x800 [ 29.945828] ? copy_msghdr_from_user+0x3b0/0x3b0 [ 29.950585] ? __lock_acquire+0x5fc/0x3f20 [ 29.954813] ? __dentry_kill+0x3f7/0x550 [ 29.958860] ? trace_hardirqs_on+0x10/0x10 [ 29.963083] ? rcu_lockdep_current_cpu_online+0xed/0x140 [ 29.968529] ? dentry_free+0xc6/0x120 [ 29.972407] ? rcu_read_lock_sched_held+0x16c/0x1d0 [ 29.977405] ? kmem_cache_free+0x23a/0x2b0 [ 29.981621] ? mntput_no_expire+0xc7/0x910 [ 29.985837] ? lock_acquire+0x170/0x3f0 [ 29.989804] ? __fdget+0x167/0x1f0 [ 29.993342] ? sockfd_lookup_light+0xb2/0x160 [ 29.997825] __sys_sendmsg+0xa3/0x120 [ 30.001771] ? SyS_shutdown+0x160/0x160 [ 30.005733] SyS_sendmsg+0x27/0x40 [ 30.009268] ? __sys_sendmsg+0x120/0x120 [ 30.013326] do_syscall_64+0x1d5/0x640 [ 30.017207] entry_SYSCALL_64_after_hwframe+0x46/0xbb [ 30.022487] RIP: 0033:0x440909 [ 30.025670] RSP: 002b:00007fff3b759b28 EFLAGS: 00000246 ORIG_RAX: 000000000000002e [ 30.033388] RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440909 [ 30.040640] RDX: 0000000000000000 RSI: 0000000020000100 RDI: 0000000000000003 [ 30.048005] RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8 [ 30.055261] R10: 00000000