[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c.
[....] Starting OpenBSD Secure Shell server: sshd[   13.228517] random: sshd: uninitialized urandom read (32 bytes read)
[?25l[?1c7[ ok 8[?25h[?0c.

Debian GNU/Linux 7 syzkaller ttyS0

syzkaller login: [   19.911057] random: sshd: uninitialized urandom read (32 bytes read)
[   20.331019] random: sshd: uninitialized urandom read (32 bytes read)
[   21.293055] random: sshd: uninitialized urandom read (32 bytes read)
[   30.244494] random: sshd: uninitialized urandom read (32 bytes read)
Warning: Permanently added '10.128.0.56' (ECDSA) to the list of known hosts.
[   35.697302] random: sshd: uninitialized urandom read (32 bytes read)
executing program
executing program
[   35.914387] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
[   35.922683] IP: [<ffffffff836be91c>] l2tp_session_free+0x11c/0x200
[   35.929096] PGD 1cb259067 [   35.931734] PUD 1cb25e067 
PMD 0 [   35.935214] 
[   35.936832] Oops: 0002 [#1] PREEMPT SMP KASAN
[   35.941300] Dumping ftrace buffer:
[   35.944808]    (ftrace buffer empty)
[   35.948491] Modules linked in:
[   35.951807] CPU: 0 PID: 3815 Comm: syz-executor827 Not tainted 4.9.116-g52be322 #17
[   35.959573] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   35.968909] task: ffff8801b75e9800 task.stack: ffff8801d9168000
[   35.974933] RIP: 0010:[<ffffffff836be91c>]  [<ffffffff836be91c>] l2tp_session_free+0x11c/0x200
[   35.983788] RSP: 0018:ffff8801d916fca0  EFLAGS: 00010246
[   35.989217] RAX: dffffc0000000000 RBX: ffff8801cb3d7b80 RCX: 0000000000000000
[   35.996461] RDX: 1ffff100394b8eb0 RSI: ffffffff836be8f1 RDI: ffff8801ca5c7580
[   36.003712] RBP: ffff8801d916fcc0 R08: ffff8801b75ea0e8 R09: 0000000000000000
[   36.010957] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801ca5c7400
[   36.018199] R13: ffff8801cb3d7b88 R14: 0000000000000000 R15: ffffffff83014be0
[   36.025445] FS:  00000000025d0880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
[   36.033642] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   36.039493] CR2: 0000000000000080 CR3: 00000001cb03c000 CR4: 00000000001606f0
[   36.046733] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   36.053975] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   36.061217] Stack:
[   36.063342]  ffff8801d9331100 ffff8801cb3d7b80 ffff8801d93314d0 ffff8801d93313d8
[   36.071343]  ffff8801d916fce8 ffffffff836c6202 ffff8801d9331540 ffff8801d9331100
[   36.079848]  ffffffff836c6130 ffff8801d916fd20 ffffffff83022095 ffff8801d9331540
[   36.087841] Call Trace:
[   36.090410]  [<ffffffff836c6202>] pppol2tp_session_destruct+0xd2/0x110
[   36.097061]  [<ffffffff836c6130>] ? pppol2tp_seq_start+0x4e0/0x4e0
[   36.103366]  [<ffffffff83022095>] __sk_destruct+0x55/0x590
[   36.108961]  [<ffffffff83014be0>] ? sock_release+0x1c0/0x1c0
[   36.114729]  [<ffffffff83029b23>] sk_destruct+0x63/0x80
[   36.120065]  [<ffffffff83029b8f>] __sk_free+0x4f/0x220
[   36.125315]  [<ffffffff83029d8b>] sk_free+0x2b/0x40
[   36.130304]  [<ffffffff836c9509>] pppol2tp_release+0x239/0x2e0
[   36.136250]  [<ffffffff83014ab6>] sock_release+0x96/0x1c0
[   36.141758]  [<ffffffff83014bf6>] sock_close+0x16/0x20
[   36.147007]  [<ffffffff81578453>] __fput+0x263/0x700
[   36.152083]  [<ffffffff81578975>] ____fput+0x15/0x20
[   36.157160]  [<ffffffff8119838c>] task_work_run+0x10c/0x180
[   36.162846]  [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120
[   36.169146]  [<ffffffff810064d4>] do_syscall_64+0x364/0x490
[   36.174828]  [<ffffffff839fbc13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
[   36.181723] 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 65 01 ca fd 4c 89 ea 48 b8 00 
[   36.208513] RIP  [<ffffffff836be91c>] l2tp_session_free+0x11c/0x200
[   36.215010]  RSP <ffff8801d916fca0>
[   36.218606] CR2: 0000000000000080
[   36.222222] ---[ end trace 5789cfe70567402b ]---
[   36.226985] Kernel panic - not syncing: Fatal exception
[   36.232743] Dumping ftrace buffer:
[   36.236256]    (ftrace buffer empty)
[   36.239943] Kernel Offset: disabled
[   36.243543] Rebooting in 86400 seconds..