[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.375147] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [ 14.185290] random: sshd: uninitialized urandom read (32 bytes read) Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 14.581453] random: sshd: uninitialized urandom read (32 bytes read) [ 15.389466] random: sshd: uninitialized urandom read (32 bytes read) [ 15.528187] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.32' (ECDSA) to the list of known hosts. [ 21.006827] random: sshd: uninitialized urandom read (32 bytes read) [ 21.095027] [ 21.096670] ====================================================== [ 21.102960] [ INFO: possible circular locking dependency detected ] [ 21.109351] 4.9.109-ga4230be #48 Not tainted [ 21.113731] ------------------------------------------------------- [ 21.120200] syz-executor240/3796 is trying to acquire lock: [ 21.125891] (sk_lock-AF_INET){+.+.+.}, at: [] do_ip_setsockopt.isra.13+0x12a/0x2b10 [ 21.135687] but task is already holding lock: [ 21.140326] (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 [ 21.148104] which lock already depends on the new lock. [ 21.148104] [ 21.155107] [ 21.155107] the existing dependency chain (in reverse order) is: [ 21.162700] -> #1 (rtnl_mutex){+.+.+.}: [ 21.167314] lock_acquire+0x130/0x3e0 [ 21.171617] mutex_lock_nested+0xc0/0x870 [ 21.176256] rtnl_lock+0x17/0x20 [ 21.180125] mrtsock_destruct+0x3b/0x1e0 [ 21.184690] ip_ra_control+0x2c2/0x420 [ 21.189072] do_ip_setsockopt.isra.13+0x15ff/0x2b10 [ 21.194582] ip_setsockopt+0x3a/0xb0 [ 21.198792] raw_setsockopt+0xb7/0xd0 [ 21.203097] sock_common_setsockopt+0x9a/0xe0 [ 21.208086] SyS_setsockopt+0x166/0x260 [ 21.212556] do_syscall_64+0x1a6/0x490 [ 21.216948] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 21.222549] -> #0 (sk_lock-AF_INET){+.+.+.}: [ 21.227583] __lock_acquire+0x3019/0x4070 [ 21.232232] lock_acquire+0x130/0x3e0 [ 21.236526] lock_sock_nested+0xc6/0x120 [ 21.241083] do_ip_setsockopt.isra.13+0x12a/0x2b10 [ 21.246505] ip_setsockopt+0x3a/0xb0 [ 21.250712] udp_setsockopt+0x4a/0x90 [ 21.255005] sock_common_setsockopt+0x9a/0xe0 [ 21.260000] SyS_setsockopt+0x166/0x260 [ 21.264469] do_syscall_64+0x1a6/0x490 [ 21.268850] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 21.274447] [ 21.274447] other info that might help us debug this: [ 21.274447] [ 21.282558] Possible unsafe locking scenario: [ 21.282558] [ 21.288593] CPU0 CPU1 [ 21.293236] ---- ---- [ 21.297964] lock(rtnl_mutex); [ 21.301476] lock(sk_lock-AF_INET); [ 21.307918] lock(rtnl_mutex); [ 21.313927] lock(sk_lock-AF_INET); [ 21.317866] [ 21.317866] *** DEADLOCK *** [ 21.317866] [ 21.323904] 1 lock held by syz-executor240/3796: [ 21.328637] #0: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 [ 21.337018] [ 21.337018] stack backtrace: [ 21.341501] CPU: 1 PID: 3796 Comm: syz-executor240 Not tainted 4.9.109-ga4230be #48 [ 21.349357] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 21.358784] ffff8801da3b7758 ffffffff81eb3e29 ffffffff855e7b60 ffffffff8559cef0 [ 21.366765] ffffffff855e7b60 ffff8801c81508e8 ffff8801c8150000 ffff8801da3b77a0 [ 21.374771] ffffffff814262d4 0000000000000001 00000000c8150000 0000000000000001 [ 21.382775] Call Trace: [ 21.385338] [] dump_stack+0xc1/0x128 [ 21.390676] [] print_circular_bug.cold.51+0x1bd/0x27d [ 21.397487] [] __lock_acquire+0x3019/0x4070 [ 21.403432] [] ? debug_check_no_locks_freed+0x210/0x210 [ 21.410424] [] ? mark_held_locks+0xc7/0x130 [ 21.416374] [] ? mutex_lock_nested+0x572/0x870 [ 21.422589] [] lock_acquire+0x130/0x3e0 [ 21.428186] [] ? do_ip_setsockopt.isra.13+0x12a/0x2b10 [ 21.435099] [] lock_sock_nested+0xc6/0x120 [ 21.440959] [] ? do_ip_setsockopt.isra.13+0x12a/0x2b10 [ 21.447867] [] do_ip_setsockopt.isra.13+0x12a/0x2b10 [ 21.454621] [] ? ip_ra_control+0x420/0x420 [ 21.460503] [] ? get_empty_filp+0x8f/0x380 [ 21.466372] [] ? alloc_file+0x20/0x350 [ 21.471895] [] ? sock_alloc_file+0x151/0x330 [ 21.477934] [] ? sock_map_fd+0x34/0x70 [ 21.483462] [] ? SyS_socket+0x10f/0x1b0 [ 21.489067] [] ? do_syscall_64+0x1a6/0x490 [ 21.494932] [] ? entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 21.502015] [] ? debug_check_no_locks_freed+0x210/0x210 [ 21.509007] [] ? debug_check_no_locks_freed+0x210/0x210 [ 21.516019] [] ? check_preemption_disabled+0x3b/0x170 [ 21.522844] [] ? sock_has_perm+0x1c2/0x3e0 [ 21.528715] [] ? sock_has_perm+0x292/0x3e0 [ 21.534587] [] ? sock_has_perm+0x9f/0x3e0 [ 21.540368] [] ? selinux_file_send_sigiotask+0x310/0x310 [ 21.547460] [] ? selinux_netlbl_socket_setsockopt+0x8c/0x340 [ 21.554896] [] ? selinux_netlbl_sock_rcv_skb+0x480/0x480 [ 21.561981] [] ip_setsockopt+0x3a/0xb0 [ 21.567493] [] udp_setsockopt+0x4a/0x90 [ 21.573104] [] sock_common_setsockopt+0x9a/0xe0 [ 21.579437] [] SyS_setsockopt+0x166/0x260 [ 21.585368] [] ? SyS_recv+0x40/0x40 [ 21.590627] [] ? __do_page_fault+0x183/0xd50 [ 21.