[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 12.376443] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 16.051620] random: sshd: uninitialized urandom read (32 bytes read) [ 16.466961] random: sshd: uninitialized urandom read (32 bytes read) [ 16.966289] random: sshd: uninitialized urandom read (32 bytes read) [ 17.090249] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.31' (ECDSA) to the list of known hosts. [ 22.546006] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 22.770606] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 22.778858] IP: [<ffffffff836bf91c>] l2tp_session_free+0x11c/0x200 [ 22.785307] PGD 1cb16f067 [ 22.787955] PUD 1cbb86067 PMD 0 [ 22.791444] [ 22.793087] Oops: 0002 [#1] PREEMPT SMP KASAN [ 22.797561] Dumping ftrace buffer: [ 22.801078] (ftrace buffer empty) [ 22.804766] Modules linked in: [ 22.808065] CPU: 1 PID: 3795 Comm: syz-executor712 Not tainted 4.9.117-g8b21e85 #71 [ 22.815836] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 22.825172] task: ffff8801b9da6000 task.stack: ffff8801b67f0000 [ 22.832887] RIP: 0010:[<ffffffff836bf91c>] [<ffffffff836bf91c>] l2tp_session_free+0x11c/0x200 [ 22.841753] RSP: 0018:ffff8801b67f7ca0 EFLAGS: 00010246 [ 22.847176] RAX: dffffc0000000000 RBX: ffff8801cb5aec80 RCX: 0000000000000000 [ 22.854418] RDX: 1ffff10036d1d880 RSI: ffffffff836bf8f1 RDI: ffff8801b68ec400 [ 22.861663] RBP: ffff8801b67f7cc0 R08: ffff8801b9da68e8 R09: 0000000000000000 [ 22.868909] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b68ec280 [ 22.876153] R13: ffff8801cb5aec88 R14: 0000000000000000 R15: ffffffff83015be0 [ 22.883399] FS: 000000000153e880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 22.891600] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 22.897457] CR2: 0000000000000080 CR3: 00000001c0ef8000 CR4: 00000000001606f0 [ 22.904704] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 22.911947] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 22.919196] Stack: [ 22.921325] ffff8801b666cc80 ffff8801cb5aec80 ffff8801b666d050 ffff8801b666cf58 [ 22.929313] ffff8801b67f7ce8 ffffffff836c7202 ffff8801b666d0c0 ffff8801b666cc80 [ 22.937307] ffffffff836c7130 ffff8801b67f7d20 ffffffff83023095 ffff8801b666d0c0 [ 22.945315] Call Trace: [ 22.947884] [<ffffffff836c7202>] pppol2tp_session_destruct+0xd2/0x110 [ 22.954534] [<ffffffff836c7130>] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 22.960850] [<ffffffff83023095>] __sk_destruct+0x55/0x590 [ 22.966450] [<ffffffff83015be0>] ? sock_release+0x1c0/0x1c0 [ 22.972224] [<ffffffff8302ab23>] sk_destruct+0x63/0x80 [ 22.977563] [<ffffffff8302ab8f>] __sk_free+0x4f/0x220 [ 22.982814] [<ffffffff8302ad8b>] sk_free+0x2b/0x40 [ 22.987803] [<ffffffff836ca509>] pppol2tp_release+0x239/0x2e0 [ 22.993750] [<ffffffff83015ab6>] sock_release+0x96/0x1c0 [ 22.999269] [<ffffffff83015bf6>] sock_close+0x16/0x20 [ 23.004521] [<ffffffff81578693>] __fput+0x263/0x700 [ 23.009597] [<ffffffff81578bb5>] ____fput+0x15/0x20 [ 23.014676] [<ffffffff8119838c>] task_work_run+0x10c/0x180 [ 23.020363] [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 [ 23.026658] [<ffffffff810064d4>] do_syscall_64+0x364/0x490 [ 23.032343] [<ffffffff839fcc13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 23.039242] 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 <f0> 41 ff 8e 80 00 00 00 74 69 e8 e5 f1 c9 fd 4c 89 ea 48 b8 00 [ 23.066104] RIP [<ffffffff836bf91c>] l2tp_session_free+0x11c/0x200 [ 23.072610] RSP <ffff8801b67f7ca0> [ 23.076207] CR2: 0000000000000080 [ 23.079853] ---[ end trace a5824faf2983ff91 ]--- [ 23.084609] Kernel panic - not syncing: Fatal exception [ 23.090267] Dumping ftrace buffer: [ 23.093793] (ftrace buffer empty) [ 23.097481] Kernel Offset: disabled [ 23.101083] Rebooting in 86400 seconds..