[ OK ] Started Getty on tty2. [ OK ] Started Getty on tty1. [ OK ] Started Serial Getty on ttyS0. [ OK ] Reached target Login Prompts. [ OK ] Reached target Multi-User System. [ 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 '10.128.0.243' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 31.586674] [ 31.588468] ============================= [ 31.592623] WARNING: suspicious RCU usage [ 31.598189] 4.14.214-syzkaller #0 Not tainted [ 31.603146] ----------------------------- [ 31.607751] net/tipc/bearer.c:177 suspicious rcu_dereference_protected() usage! [ 31.616523] [ 31.616523] other info that might help us debug this: [ 31.616523] [ 31.625541] [ 31.625541] rcu_scheduler_active = 2, debug_locks = 1 [ 31.632292] 2 locks held by syz-executor527/7982: [ 31.637306] #0: (cb_lock){++++}, at: [] genl_rcv+0x15/0x40 [ 31.645851] #1: (genl_mutex){+.+.}, at: [] genl_rcv_msg+0x112/0x140 [ 31.654015] [ 31.654015] stack backtrace: [ 31.658609] CPU: 1 PID: 7982 Comm: syz-executor527 Not tainted 4.14.214-syzkaller #0 [ 31.666482] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 31.675828] Call Trace: [ 31.678425] dump_stack+0x1b2/0x283 [ 31.682120] tipc_bearer_find+0x1ff/0x2f0 [ 31.686251] tipc_nl_compat_link_set+0x40b/0xb90 [ 31.691449] ? __alloc_skb+0x3dc/0x510 [ 31.695510] tipc_nl_compat_doit+0x192/0x5d0 [ 31.700016] ? tipc_nl_compat_link_set+0xb90/0xb90 [ 31.704931] ? security_capable+0x88/0xb0 [ 31.709064] ? ns_capable_common+0x127/0x150 [ 31.713457] tipc_nl_compat_recv+0xa0b/0xae0 [ 31.717857] ? tipc_nl_compat_dumpit+0x7a0/0x7a0 [ 31.722606] ? tipc_nl_node_dump+0xc20/0xc20 [ 31.726995] ? __tipc_add_link_prop.isra.0+0x190/0x190 [ 31.732283] ? lock_downgrade+0x740/0x740 [ 31.736419] genl_family_rcv_msg+0x572/0xb20 [ 31.740808] ? __lock_acquire+0x5fc/0x3f20 [ 31.745196] ? genl_rcv+0x40/0x40 [ 31.748631] ? __ww_mutex_wakeup_for_backoff+0x210/0x210 [ 31.754074] ? trace_hardirqs_on+0x10/0x10 [ 31.758289] ? sock_sendmsg+0xb5/0x100 [ 31.762161] genl_rcv_msg+0xaf/0x140 [ 31.765858] netlink_rcv_skb+0x125/0x390 [ 31.769901] ? genl_family_rcv_msg+0xb20/0xb20 [ 31.774462] ? netlink_ack+0x9a0/0x9a0 [ 31.778339] ? lock_acquire+0x170/0x3f0 [ 31.782296] genl_rcv+0x24/0x40 [ 31.785559] netlink_unicast+0x437/0x610 [ 31.789601] ? netlink_sendskb+0xd0/0xd0 [ 31.793641] ? __check_object_size+0x179/0x22c [ 31.798217] netlink_sendmsg+0x62e/0xb80 [ 31.802272] ? nlmsg_notify+0x170/0x170 [ 31.806227] ? kernel_recvmsg+0x210/0x210 [ 31.813853] ? security_socket_sendmsg+0x83/0xb0 [ 31.818589] ? nlmsg_notify+0x170/0x170 [ 31.822542] sock_sendmsg+0xb5/0x100 [ 31.826503] ___sys_sendmsg+0x6c8/0x800 [ 31.830857] ? copy_msghdr_from_user+0x3b0/0x3b0 [ 31.835625] ? trace_hardirqs_on+0x10/0x10 [ 31.839842] ? trace_hardirqs_on+0x10/0x10 [ 31.844067] ? apparmor_file_alloc_security+0x129/0x800 [ 31.849418] ? rcu_lockdep_current_cpu_online+0xed/0x140 [ 31.854872] ? __lockdep_init_map+0x100/0x560 [ 31.859813] ? __fd_install+0x1ec/0x5c0 [ 31.863798] ? lock_acquire+0x170/0x3f0 [ 31.867782] ? lock_downgrade+0x740/0x740 [ 31.871917] ? __fdget+0x167/0x1f0 [ 31.875482] ? sockfd_lookup_light+0xb2/0x160 [ 31.879991] __sys_sendmsg+0xa3/0x120 [ 31.883794] ? SyS_shutdown+0x160/0x160 [ 31.887758] ? move_addr_to_kernel+0x60/0x60 [ 31.894027] SyS_sendmsg+0x27/0x40 [ 31.897548] ? __sys_sendmsg+0x120/0x120 [ 31.901591] do_syscall_64+0x1d5/0x640 [ 31.905483] entry_SYSCALL_64_after_hwframe+0x46/0xbb [ 31.910659] RIP: 0033:0x440979 [ 31.913839] RSP: 002b:00007ffd1ef57e58 EFLAGS: 00000246 ORIG_RAX: 000000000000002e [ 31.921699] RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440979 [ 31.928993] RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003 [ 31.936347] RBP: 00000000006ca018 R08: 0