[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c.
[....] Starting OpenBSD Secure Shell server: sshd[   11.988605] random: sshd: uninitialized urandom read (32 bytes read)
[?25l[?1c7[ ok 8[?25h[?0c.

Debian GNU/Linux 7 syzkaller ttyS0

syzkaller login: [   16.411013] random: sshd: uninitialized urandom read (32 bytes read)
[   16.826817] random: sshd: uninitialized urandom read (32 bytes read)
[   17.754861] random: sshd: uninitialized urandom read (32 bytes read)
[   25.874427] random: sshd: uninitialized urandom read (32 bytes read)
Warning: Permanently added '10.128.0.54' (ECDSA) to the list of known hosts.
[   31.308164] random: sshd: uninitialized urandom read (32 bytes read)
executing program
executing program
[   31.517839] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
[   31.526060] IP: [<ffffffff836bcd0c>] l2tp_session_free+0x11c/0x200
[   31.532473] PGD 1c040e067 [   31.535110] PUD 1bb8ed067 
PMD 0 [   31.538585] 
[   31.540204] Oops: 0002 [#1] PREEMPT SMP KASAN
[   31.544671] Dumping ftrace buffer:
[   31.548211]    (ftrace buffer empty)
[   31.551892] Modules linked in:
[   31.555174] CPU: 1 PID: 3797 Comm: syz-executor593 Not tainted 4.9.113-g47bbcd6 #62
[   31.562936] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   31.572264] task: ffff8801b9124800 task.stack: ffff8801b62f0000
[   31.578288] RIP: 0010:[<ffffffff836bcd0c>]  [<ffffffff836bcd0c>] l2tp_session_free+0x11c/0x200
[   31.587127] RSP: 0018:ffff8801b62f7ca0  EFLAGS: 00010246
[   31.592543] RAX: dffffc0000000000 RBX: ffff8801c61d2a00 RCX: 0000000000000000
[   31.599794] RDX: 1ffff10038c21660 RSI: ffffffff836bcce1 RDI: ffff8801c610b300
[   31.607035] RBP: ffff8801b62f7cc0 R08: ffff8801b91250e8 R09: 0000000000000000
[   31.614287] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c610b180
[   31.621526] R13: ffff8801c61d2a08 R14: 0000000000000000 R15: ffffffff83013be0
[   31.628769] FS:  0000000001b43880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
[   31.636964] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   31.642816] CR2: 0000000000000080 CR3: 00000001c04e5000 CR4: 00000000001606f0
[   31.650056] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   31.657299] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   31.664539] Stack:
[   31.666666]  ffff8801d9679100 ffff8801c61d2a00 ffff8801d96794d0 ffff8801d96793d8
[   31.674642]  ffff8801b62f7ce8 ffffffff836c45f2 ffff8801d9679540 ffff8801d9679100
[   31.682612]  ffffffff836c4520 ffff8801b62f7d20 ffffffff83021095 ffff8801d9679540
[   31.690619] Call Trace:
[   31.693182]  [<ffffffff836c45f2>] pppol2tp_session_destruct+0xd2/0x110
[   31.699818]  [<ffffffff836c4520>] ? pppol2tp_seq_start+0x4e0/0x4e0
[   31.706108]  [<ffffffff83021095>] __sk_destruct+0x55/0x590
[   31.711703]  [<ffffffff83013be0>] ? sock_release+0x1c0/0x1c0
[   31.717471]  [<ffffffff83028b23>] sk_destruct+0x63/0x80
[   31.722804]  [<ffffffff83028b8f>] __sk_free+0x4f/0x220
[   31.728062]  [<ffffffff83028d8b>] sk_free+0x2b/0x40
[   31.733046]  [<ffffffff836c78f9>] pppol2tp_release+0x239/0x2e0
[   31.738990]  [<ffffffff83013ab6>] sock_release+0x96/0x1c0
[   31.749706]  [<ffffffff83013bf6>] sock_close+0x16/0x20
[   31.754955]  [<ffffffff815782e3>] __fput+0x263/0x700
[   31.760029]  [<ffffffff81578805>] ____fput+0x15/0x20
[   31.765104]  [<ffffffff8119838c>] task_work_run+0x10c/0x180
[   31.770788]  [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120
[   31.777347]  [<ffffffff810064d4>] do_syscall_64+0x364/0x490
[   31.783040]  [<ffffffff839f9f93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
[   31.789957] 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 55 1d ca fd 4c 89 ea 48 b8 00 
[   31.817125] RIP  [<ffffffff836bcd0c>] l2tp_session_free+0x11c/0x200
[   31.823652]  RSP <ffff8801b62f7ca0>
[   31.827258] CR2: 0000000000000080
[   31.830787] ---[ end trace 6fc2a838ae7cc339 ]---
[   31.835536] Kernel panic - not syncing: Fatal exception
[   31.841287] Dumping ftrace buffer:
[   31.844798]    (ftrace buffer empty)
[   31.848482] Kernel Offset: disabled
[   31.852083] Rebooting in 86400 seconds..