[ 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 '10.128.0.63' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 27.344060] [ 27.345770] ============================= [ 27.349896] WARNING: suspicious RCU usage [ 27.354273] 4.14.277-syzkaller #0 Not tainted [ 27.358759] ----------------------------- [ 27.363047] net/tipc/bearer.c:177 suspicious rcu_dereference_protected() usage! [ 27.370601] [ 27.370601] other info that might help us debug this: [ 27.370601] [ 27.378814] [ 27.378814] rcu_scheduler_active = 2, debug_locks = 1 [ 27.385670] 2 locks held by syz-executor944/7969: [ 27.390496] #0: (cb_lock){++++}, at: [] genl_rcv+0x15/0x40 [ 27.398415] #1: (genl_mutex){+.+.}, at: [] genl_rcv_msg+0x112/0x140 [ 27.406643] [ 27.406643] stack backtrace: [ 27.411278] CPU: 1 PID: 7969 Comm: syz-executor944 Not tainted 4.14.277-syzkaller #0 [ 27.419136] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.428472] Call Trace: [ 27.431042] dump_stack+0x1b2/0x281 [ 27.434651] tipc_bearer_find+0x1ff/0x2f0 [ 27.438777] tipc_nl_compat_link_set+0x40b/0xb90 [ 27.443512] ? __alloc_skb+0x3dc/0x510 [ 27.447377] tipc_nl_compat_doit+0x192/0x5d0 [ 27.451761] ? tipc_nl_compat_link_set+0xb90/0xb90 [ 27.456668] ? security_capable+0x88/0xb0 [ 27.460794] ? ns_capable_common+0x127/0x150 [ 27.465177] tipc_nl_compat_recv+0xa0b/0xae0 [ 27.469561] ? tipc_nl_compat_dumpit+0x7a0/0x7a0 [ 27.474293] ? tipc_nl_node_dump+0xc20/0xc20 [ 27.478677] ? __tipc_add_link_prop.isra.0+0x190/0x190 [ 27.483930] ? lock_downgrade+0x740/0x740 [ 27.488060] genl_family_rcv_msg+0x572/0xb20 [ 27.492447] ? __lock_acquire+0x5fc/0x3f20 [ 27.496656] ? genl_rcv+0x40/0x40 [ 27.500088] ? __ww_mutex_wakeup_for_backoff+0x210/0x210 [ 27.505514] ? __kmalloc_node_track_caller+0x4c/0x70 [ 27.510612] ? trace_hardirqs_on+0x10/0x10 [ 27.514828] genl_rcv_msg+0xaf/0x140 [ 27.518519] netlink_rcv_skb+0x125/0x390 [ 27.522554] ? genl_family_rcv_msg+0xb20/0xb20 [ 27.527111] ? netlink_ack+0x9a0/0x9a0 [ 27.530973] ? lock_acquire+0x170/0x3f0 [ 27.534926] genl_rcv+0x24/0x40 [ 27.538182] netlink_unicast+0x437/0x610 [ 27.542221] ? netlink_sendskb+0xd0/0xd0 [ 27.546260] ? __check_object_size+0x179/0x230 [ 27.550821] netlink_sendmsg+0x648/0xbc0 [ 27.554862] ? nlmsg_notify+0x1b0/0x1b0 [ 27.558812] ? kernel_recvmsg+0x210/0x210 [ 27.562938] ? security_socket_sendmsg+0x83/0xb0 [ 27.567669] ? nlmsg_notify+0x1b0/0x1b0 [ 27.571618] sock_sendmsg+0xb5/0x100 [ 27.575309] ___sys_sendmsg+0x6c8/0x800 [ 27.579262] ? copy_msghdr_from_user+0x3b0/0x3b0 [ 27.583994] ? __lock_acquire+0x5fc/0x3f20 [ 27.588208] ? __dentry_kill+0x3f7/0x550 [ 27.592248] ? trace_hardirqs_on+0x10/0x10 [ 27.596461] ? rcu_lockdep_current_cpu_online+0xed/0x140 [ 27.601887] ? dentry_free+0xc6/0x120 [ 27.605667] ? rcu_read_lock_sched_held+0x16c/0x1d0 [ 27.610658] ? kmem_cache_free+0x23a/0x2b0 [ 27.614869] ? mntput_no_expire+0xc7/0x910 [ 27.619079] ? lock_acquire+0x170/0x3f0 [ 27.623028] ? __fdget+0x167/0x1f0 [ 27.626543] ? sockfd_lookup_light+0xb2/0x160 [ 27.631015] __sys_sendmsg+0xa3/0x120 [ 27.634790] ? SyS_shutdown+0x160/0x160 [ 27.638747] SyS_sendmsg+0x27/0x40 [ 27.642262] ? __sys_sendmsg+0x120/0x120 [ 27.646296] do_syscall_64+0x1d5/0x640 [ 27.650161] entry_SYSCALL_64_after_hwframe+0x46/0xbb [ 27.655324] RIP: 0033:0x7f20bbe2ab89 [ 27.659011] RSP: 002b:00007ffc51e91548 EFLAGS: 00000246 ORIG_RAX: 000000000000002e [ 27.666694] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f20bbe2ab89 [ 27.673938] RDX: 0000000000000000 RSI: 0000000020000240 RDI: 0000000000000003 [ 27.681182] RBP: 00007f20bbdee5f0 R08: 0000000000000000 R09: 0000000000000000 [ 27.688427] R10: 0000000000001800 R11: 0000000000000246 R12: 00007f20bbdee680