[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 12.210707] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 21.091823] random: sshd: uninitialized urandom read (32 bytes read) [ 21.600592] random: sshd: uninitialized urandom read (32 bytes read) [ 22.048102] random: sshd: uninitialized urandom read (32 bytes read) [ 27.408340] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.4' (ECDSA) to the list of known hosts. [ 32.858752] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 33.042992] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 33.051234] IP: [] l2tp_session_free+0x11c/0x200 [ 33.057645] PGD 1c8fcf067 [ 33.060286] PUD 1baaf7067 PMD 0 [ 33.063792] [ 33.065420] Oops: 0002 [#1] PREEMPT SMP KASAN [ 33.069895] Dumping ftrace buffer: [ 33.073403] (ftrace buffer empty) [ 33.077085] Modules linked in: [ 33.080368] CPU: 0 PID: 3797 Comm: syz-executor151 Not tainted 4.9.117-g8b21e85 #71 [ 33.088130] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 33.097457] task: ffff8801bb340000 task.stack: ffff8801b85c0000 [ 33.103482] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 33.112348] RSP: 0018:ffff8801b85c7ca0 EFLAGS: 00010246 [ 33.117770] RAX: dffffc0000000000 RBX: ffff8801b8e19b80 RCX: 0000000000000000 [ 33.125027] RDX: 1ffff100371fe210 RSI: ffffffff836bf8f1 RDI: ffff8801b8ff1080 [ 33.132273] RBP: ffff8801b85c7cc0 R08: ffff8801bb3408e8 R09: 0000000000000000 [ 33.139526] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b8ff0f00 [ 33.146769] R13: ffff8801b8e19b88 R14: 0000000000000000 R15: ffffffff83015be0 [ 33.154014] FS: 000000000204d880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 33.162224] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 33.168083] CR2: 0000000000000080 CR3: 00000001ca8df000 CR4: 00000000001606f0 [ 33.175325] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 33.182566] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 33.189807] Stack: [ 33.191926] ffff8801d9b7c400 ffff8801b8e19b80 ffff8801d9b7c7d0 ffff8801d9b7c6d8 [ 33.199917] ffff8801b85c7ce8 ffffffff836c7202 ffff8801d9b7c840 ffff8801d9b7c400 [ 33.207916] ffffffff836c7130 ffff8801b85c7d20 ffffffff83023095 ffff8801d9b7c840 [ 33.215879] Call Trace: [ 33.218449] [] pppol2tp_session_destruct+0xd2/0x110 [ 33.225103] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 33.231404] [] __sk_destruct+0x55/0x590 [ 33.237014] [] ? sock_release+0x1c0/0x1c0 [ 33.242822] [] sk_destruct+0x63/0x80 [ 33.248172] [] __sk_free+0x4f/0x220 [ 33.253461] [] sk_free+0x2b/0x40 [ 33.258460] [] pppol2tp_release+0x239/0x2e0 [ 33.264403] [] sock_release+0x96/0x1c0 [ 33.269913] [] sock_close+0x16/0x20 [ 33.275165] [] __fput+0x263/0x700 [ 33.280256] [] ____fput+0x15/0x20 [ 33.285354] [] task_work_run+0x10c/0x180 [ 33.291036] [] exit_to_usermode_loop+0xfc/0x120 [ 33.297325] [] do_syscall_64+0x364/0x490 [ 33.303009] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 33.309917] Code: 49 8d bc 24 80 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 c6 00 00 00 4d 8b b4 24 80 01 00 00 41 ff 8e 80 00 00 00 74 69 e8 e5 f1 c9 fd 4c 89 ea 48 b8 00 [ 33.336930] RIP [] l2tp_session_free+0x11c/0x200 [ 33.343426] RSP [ 33.347020] CR2: 0000000000000080 [ 33.350607] ---[ end trace 439782a74b0cc1b9 ]--- [ 33.355385] Kernel panic - not syncing: Fatal exception [ 33.361042] Dumping ftrace buffer: [ 33.364556] (ftrace buffer empty) [ 33.368239] Kernel Offset: disabled [ 33.371836] Rebooting in 86400 seconds..