[ OK ] Reached target Login Prompts. [ OK ] Started System Logging Service. [ OK ] Started OpenBSD Secure Shell server. [ OK ] Listening on Load/Save RF Kill Switch Status /dev/rfkill Watch. [ OK ] Reached target Multi-User System. [ OK ] Reached target Graphical Interface. Starting Update UTMP about System Runlevel Changes... [ OK ] Started Update UTMP about System Runlevel Changes. Starting Load/Save RF Kill Switch Status... [ OK ] Started Load/Save RF Kill Switch Status. Debian GNU/Linux 9 syzkaller ttyS0 Warning: Permanently added '10.128.1.123' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 27.094822] [ 27.096498] ============================= [ 27.101654] WARNING: suspicious RCU usage [ 27.105790] 4.14.290-syzkaller #0 Not tainted [ 27.110859] ----------------------------- [ 27.115009] net/tipc/bearer.c:177 suspicious rcu_dereference_protected() usage! [ 27.123005] [ 27.123005] other info that might help us debug this: [ 27.123005] [ 27.131742] [ 27.131742] rcu_scheduler_active = 2, debug_locks = 1 [ 27.138744] 2 locks held by syz-executor103/8003: [ 27.143566] #0: (cb_lock){++++}, at: [] genl_rcv+0x15/0x40 [ 27.151744] #1: (genl_mutex){+.+.}, at: [] genl_rcv_msg+0x112/0x140 [ 27.160308] [ 27.160308] stack backtrace: [ 27.164784] CPU: 0 PID: 8003 Comm: syz-executor103 Not tainted 4.14.290-syzkaller #0 [ 27.172637] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022 [ 27.181963] Call Trace: [ 27.184526] dump_stack+0x1b2/0x281 [ 27.188134] tipc_bearer_find+0x1ff/0x2f0 [ 27.192258] tipc_nl_compat_link_set+0x40b/0xb90 [ 27.196989] ? __alloc_skb+0x3dc/0x510 [ 27.200851] tipc_nl_compat_doit+0x192/0x5d0 [ 27.205237] ? tipc_nl_compat_link_set+0xb90/0xb90 [ 27.210145] ? security_capable+0x88/0xb0 [ 27.214268] ? ns_capable_common+0x127/0x150 [ 27.218657] tipc_nl_compat_recv+0xa0b/0xae0 [ 27.223039] ? tipc_nl_compat_dumpit+0x7a0/0x7a0 [ 27.227767] ? tipc_nl_node_dump+0xc20/0xc20 [ 27.232151] ? __tipc_add_link_prop.isra.0+0x190/0x190 [ 27.237404] ? lock_downgrade+0x740/0x740 [ 27.241533] genl_family_rcv_msg+0x572/0xb20 [ 27.245916] ? __lock_acquire+0x5fc/0x3f20 [ 27.250125] ? genl_rcv+0x40/0x40 [ 27.253555] ? __ww_mutex_wakeup_for_backoff+0x210/0x210 [ 27.258983] ? __kmalloc_node_track_caller+0x4c/0x70 [ 27.264062] ? trace_hardirqs_on+0x10/0x10 [ 27.268277] genl_rcv_msg+0xaf/0x140 [ 27.271965] netlink_rcv_skb+0x125/0x390 [ 27.276001] ? genl_family_rcv_msg+0xb20/0xb20 [ 27.280556] ? netlink_ack+0x9a0/0x9a0 [ 27.284415] ? lock_acquire+0x170/0x3f0 [ 27.288364] genl_rcv+0x24/0x40 [ 27.291619] netlink_unicast+0x437/0x610 [ 27.295658] ? netlink_sendskb+0xd0/0xd0 [ 27.299694] ? __check_object_size+0x179/0x230 [ 27.304254] netlink_sendmsg+0x648/0xbc0 [ 27.308291] ? nlmsg_notify+0x1b0/0x1b0 [ 27.312235] ? kernel_recvmsg+0x210/0x210 [ 27.316358] ? security_socket_sendmsg+0x83/0xb0 [ 27.321099] ? nlmsg_notify+0x1b0/0x1b0 [ 27.325050] sock_sendmsg+0xb5/0x100 [ 27.328868] ___sys_sendmsg+0x6c8/0x800 [ 27.332830] ? copy_msghdr_from_user+0x3b0/0x3b0 [ 27.337563] ? __lock_acquire+0x5fc/0x3f20 [ 27.341776] ? __dentry_kill+0x3f7/0x550 [ 27.345813] ? trace_hardirqs_on+0x10/0x10 [ 27.350022] ? rcu_lockdep_current_cpu_online+0xed/0x140 [ 27.355448] ? dentry_free+0xc6/0x120 [ 27.359222] ? rcu_read_lock_sched_held+0x16c/0x1d0 [ 27.364214] ? kmem_cache_free+0x23a/0x2b0 [ 27.368423] ? mntput_no_expire+0xc7/0x910 [ 27.372635] ? lock_acquire+0x170/0x3f0 [ 27.376599] ? __fdget+0x167/0x1f0 [ 27.380117] ? sockfd_lookup_light+0xb2/0x160 [ 27.384590] __sys_sendmsg+0xa3/0x120 [ 27.388369] ? SyS_shutdown+0x160/0x160 [ 27.392327] SyS_sendmsg+0x27/0x40 [ 27.395845] ? __sys_sendmsg+0x120/0x120 [ 27.399887] do_syscall_64+0x1d5/0x640 [ 27.403755] entry_SYSCALL_64_after_hwframe+0x46/0xbb [ 27.408920] RIP: 0033:0x7fd1b63a2b69 [ 27.412605] RSP: 002b:00007ffc94d1dbf8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e [ 27.420287] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fd1b63a2b69 [ 27.427531] RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000003 [ 27.434774] RBP: 00007fd1b63665d0 R08: 0000000000000000 R09: 0000000000000000 [ 27.442017] R10: 0000000000001800 R11: 0000000000