[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 14.678661] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 20.182186] random: sshd: uninitialized urandom read (32 bytes read) [ 20.761342] random: sshd: uninitialized urandom read (32 bytes read) [ 21.256109] random: sshd: uninitialized urandom read (32 bytes read) [ 21.398753] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.18' (ECDSA) to the list of known hosts. [ 26.889977] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 27.102409] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 27.110636] IP: [] l2tp_session_free+0x11c/0x200 [ 27.117073] PGD 1c8c93067 [ 27.119714] PUD 1c8cc4067 PMD 0 [ 27.123199] [ 27.124825] Oops: 0002 [#1] PREEMPT SMP KASAN [ 27.129293] Dumping ftrace buffer: [ 27.132804] (ftrace buffer empty) [ 27.136489] Modules linked in: [ 27.139773] CPU: 0 PID: 3802 Comm: syz-executor079 Not tainted 4.9.123-g8dd3fc2 #27 [ 27.147541] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.156871] task: ffff8801b74db000 task.stack: ffff8801b5650000 [ 27.162902] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 27.171801] RSP: 0018:ffff8801b5657ca0 EFLAGS: 00010246 [ 27.177224] RAX: dffffc0000000000 RBX: ffff8801c8d36c80 RCX: 0000000000000000 [ 27.184469] RDX: 1ffff10036aa8c80 RSI: ffffffff836c4991 RDI: ffff8801b5546400 [ 27.191714] RBP: ffff8801b5657cc0 R08: ffff8801b74db8e8 R09: 0000000000000000 [ 27.198998] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b5546280 [ 27.206248] R13: ffff8801c8d36c88 R14: 0000000000000000 R15: ffffffff8301abe0 [ 27.213599] FS: 0000000002176880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 27.221805] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 27.227660] CR2: 0000000000000080 CR3: 00000001c2c4e000 CR4: 00000000001606f0 [ 27.234907] Stack: [ 27.237034] ffff8801d94e3b80 ffff8801c8d36c80 ffff8801d94e3f50 ffff8801d94e3e58 [ 27.245128] ffff8801b5657ce8 ffffffff836cc2a2 ffff8801d94e3fc0 ffff8801d94e3b80 [ 27.253120] ffffffff836cc1d0 ffff8801b5657d20 ffffffff830280f5 ffff8801d94e3fc0 [ 27.261249] Call Trace: [ 27.263834] [] pppol2tp_session_destruct+0xd2/0x110 [ 27.270701] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 27.277110] [] __sk_destruct+0x55/0x590 [ 27.282725] [] ? sock_release+0x1c0/0x1c0 [ 27.288507] [] sk_destruct+0x63/0x80 [ 27.293855] [] __sk_free+0x4f/0x220 [ 27.299218] [] sk_free+0x2b/0x40 [ 27.304221] [] pppol2tp_release+0x239/0x2e0 [ 27.310176] [] sock_release+0x96/0x1c0 [ 27.315695] [] sock_close+0x16/0x20 [ 27.321010] [] __fput+0x263/0x700 [ 27.326102] [] ____fput+0x15/0x20 [ 27.331185] [] task_work_run+0x10c/0x180 [ 27.336881] [] exit_to_usermode_loop+0xfc/0x120 [ 27.343182] [] do_syscall_64+0x364/0x490 [ 27.348872] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.355919] 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 c3 c9 fd 4c 89 ea 48 b8 00 [ 27.383269] RIP [] l2tp_session_free+0x11c/0x200 [ 27.389783] RSP [ 27.393383] CR2: 0000000000000080 [ 27.398096] ---[ end trace 518d7ad2ca890b5f ]--- [ 27.403047] Kernel panic - not syncing: Fatal exception [ 27.408755] Dumping ftrace buffer: [ 27.412274] (ftrace buffer empty) [ 27.415960] Kernel Offset: disabled [ 27.419566] Rebooting in 86400 seconds..