[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c.
[....] Starting OpenBSD Secure Shell server: sshd[   12.009872] random: sshd: uninitialized urandom read (32 bytes read)
[?25l[?1c7[ ok 8[?25h[?0c.

Debian GNU/Linux 7 syzkaller ttyS0

syzkaller login: [   14.532084] random: sshd: uninitialized urandom read (32 bytes read)
[   14.682781] random: sshd: uninitialized urandom read (32 bytes read)
[   15.259727] random: sshd: uninitialized urandom read (32 bytes read)
[   29.688565] random: sshd: uninitialized urandom read (32 bytes read)
Warning: Permanently added '10.128.10.26' (ECDSA) to the list of known hosts.
[   35.276282] random: sshd: uninitialized urandom read (32 bytes read)
executing program
executing program
[   35.472703] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
[   35.480930] IP: [<ffffffff836c473c>] l2tp_session_free+0x11c/0x200
[   35.487367] PGD 1c3c5c067 [   35.490010] PUD 1c4934067 
PMD 0 [   35.493486] 
[   35.495108] Oops: 0002 [#1] PREEMPT SMP KASAN
[   35.499697] Dumping ftrace buffer:
[   35.503215]    (ftrace buffer empty)
[   35.506909] Modules linked in:
[   35.510340] CPU: 0 PID: 3735 Comm: syz-executor699 Not tainted 4.9.124-g09eb2ba #83
[   35.518146] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   35.527482] task: ffff8801c1784800 task.stack: ffff8801be490000
[   35.533569] RIP: 0010:[<ffffffff836c473c>]  [<ffffffff836c473c>] l2tp_session_free+0x11c/0x200
[   35.542437] RSP: 0018:ffff8801be497c98  EFLAGS: 00010246
[   35.547864] RAX: dffffc0000000000 RBX: ffff8801cb763680 RCX: 0000000000000000
[   35.555111] RDX: 1ffff10037d648d0 RSI: ffffffff836c4711 RDI: ffff8801beb24680
[   35.562356] RBP: ffff8801be497cb8 R08: ffff8801c17850e8 R09: 0000000000000000
[   35.569607] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801beb24500
[   35.576853] R13: ffff8801cb763688 R14: 0000000000000000 R15: 0000000000000000
[   35.584269] FS:  00000000017d3880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
[   35.592474] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   35.598334] CR2: 0000000000000080 CR3: 00000001c48d6000 CR4: 00000000001606f0
[   35.605812] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   35.613065] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   35.620311] Stack:
[   35.622436]  ffff8801bf2ccc80 ffff8801cb763680 ffff8801bf2cd050 ffff8801bf2ccf58
[   35.630422]  ffff8801be497ce0 ffffffff836cc022 ffff8801bf2cd0c0 ffff8801bf2ccc80
[   35.638448]  ffffffff836cbf50 ffff8801be497d18 ffffffff830281f5 ffff8801bf2cd0c0
[   35.646447] Call Trace:
[   35.649014]  [<ffffffff836cc022>] pppol2tp_session_destruct+0xd2/0x110
[   35.655662]  [<ffffffff836cbf50>] ? pppol2tp_seq_start+0x4e0/0x4e0
[   35.661959]  [<ffffffff830281f5>] __sk_destruct+0x55/0x590
[   35.667630]  [<ffffffff8302fc83>] sk_destruct+0x63/0x80
[   35.672977]  [<ffffffff8302fcef>] __sk_free+0x4f/0x220
[   35.678230]  [<ffffffff8302feeb>] sk_free+0x2b/0x40
[   35.683228]  [<ffffffff836cf329>] pppol2tp_release+0x239/0x2e0
[   35.689176]  [<ffffffff83018357>] __sock_release+0xd7/0x260
[   35.695004]  [<ffffffff830184e0>] ? __sock_release+0x260/0x260
[   35.700956]  [<ffffffff830184f9>] sock_close+0x19/0x20
[   35.706212]  [<ffffffff8157ca73>] __fput+0x263/0x700
[   35.711291]  [<ffffffff8157cf95>] ____fput+0x15/0x20
[   35.716370]  [<ffffffff8119a66c>] task_work_run+0x10c/0x180
[   35.722060]  [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120
[   35.728355]  [<ffffffff810064d4>] do_syscall_64+0x364/0x490
[   35.734045]  [<ffffffff83a019d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
[   35.740994] 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 a5 c5 c9 fd 4c 89 ea 48 b8 00 
[   35.768339] RIP  [<ffffffff836c473c>] l2tp_session_free+0x11c/0x200
[   35.774904]  RSP <ffff8801be497c98>
[   35.778516] CR2: 0000000000000080
[   35.782022] ---[ end trace d8b835a7c77a3077 ]---
[   35.786785] Kernel panic - not syncing: Fatal exception
[   35.792470] Dumping ftrace buffer:
[   35.795989]    (ftrace buffer empty)
[   35.799677] Kernel Offset: disabled
[   35.803276] Rebooting in 86400 seconds..