[....] Starting OpenBSD Secure Shell server: sshd[   14.758447] random: sshd: uninitialized urandom read (32 bytes read)
[?25l[?1c7[ ok 8[?25h[?0c.
[   14.911686] random: sshd: uninitialized urandom read (32 bytes read)
[   15.226918] random: sshd: uninitialized urandom read (32 bytes read)
[   15.830978] urandom_read: 1 callbacks suppressed
[   15.830981] random: sshd: uninitialized urandom read (32 bytes read)

Debian GNU/Linux 7 syzkaller ttyS0

Warning: Permanently added '10.128.15.195' (ECDSA) to the list of known hosts.
syzkaller login: [   21.359048] random: sshd: uninitialized urandom read (32 bytes read)
executing program
executing program
[   21.563873] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
[   21.572121] IP: [<ffffffff836c4abc>] l2tp_session_free+0x11c/0x200
[   21.578544] PGD 1b5c62067 [   21.581189] PUD 1b5c61067 
PMD 0 [   21.584674] 
[   21.586292] Oops: 0002 [#1] PREEMPT SMP KASAN
[   21.590789] Dumping ftrace buffer:
[   21.594303]    (ftrace buffer empty)
[   21.597991] Modules linked in:
[   21.601282] CPU: 0 PID: 3793 Comm: syz-executor077 Not tainted 4.9.123-g7fa8c15 #28
[   21.609050] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   21.618382] task: ffff8801b600b000 task.stack: ffff8801b5fd8000
[   21.624412] RIP: 0010:[<ffffffff836c4abc>]  [<ffffffff836c4abc>] l2tp_session_free+0x11c/0x200
[   21.633282] RSP: 0018:ffff8801b5fdfc98  EFLAGS: 00010246
[   21.638708] RAX: dffffc0000000000 RBX: ffff8801b6494c80 RCX: 0000000000000000
[   21.645985] RDX: 1ffff10036c2bd20 RSI: ffffffff836c4a91 RDI: ffff8801b615e900
[   21.653251] RBP: ffff8801b5fdfcb8 R08: ffff8801b600b8e8 R09: 0000000000000000
[   21.660500] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b615e780
[   21.667778] R13: ffff8801b6494c88 R14: 0000000000000000 R15: 0000000000000000
[   21.675028] FS:  0000000002002880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
[   21.683229] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   21.689093] CR2: 0000000000000080 CR3: 00000001b5dc0000 CR4: 00000000001606f0
[   21.696337] Stack:
[   21.698476]  ffff8801b8935500 ffff8801b6494c80 ffff8801b89358d0 ffff8801b89357d8
[   21.706481]  ffff8801b5fdfce0 ffffffff836cc3a2 ffff8801b8935940 ffff8801b8935500
[   21.714486]  ffffffff836cc2d0 ffff8801b5fdfd18 ffffffff830281f5 ffff8801b8935940
[   21.722520] Call Trace:
[   21.725088]  [<ffffffff836cc3a2>] pppol2tp_session_destruct+0xd2/0x110
[   21.731733]  [<ffffffff836cc2d0>] ? pppol2tp_seq_start+0x4e0/0x4e0
[   21.738032]  [<ffffffff830281f5>] __sk_destruct+0x55/0x590
[   21.743644]  [<ffffffff8302fc83>] sk_destruct+0x63/0x80
[   21.748987]  [<ffffffff8302fcef>] __sk_free+0x4f/0x220
[   21.754250]  [<ffffffff8302feeb>] sk_free+0x2b/0x40
[   21.759255]  [<ffffffff836cf6a9>] pppol2tp_release+0x239/0x2e0
[   21.765215]  [<ffffffff83018357>] __sock_release+0xd7/0x260
[   21.770913]  [<ffffffff830184e0>] ? __sock_release+0x260/0x260
[   21.776895]  [<ffffffff830184f9>] sock_close+0x19/0x20
[   21.782155]  [<ffffffff8157cb13>] __fput+0x263/0x700
[   21.787235]  [<ffffffff8157d035>] ____fput+0x15/0x20
[   21.792317]  [<ffffffff8119a66c>] task_work_run+0x10c/0x180
[   21.798007]  [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120
[   21.804321]  [<ffffffff810064d4>] do_syscall_64+0x364/0x490
[   21.810012]  [<ffffffff83a01d93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
[   21.816910] 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 c2 c9 fd 4c 89 ea 48 b8 00 
[   21.844071] RIP  [<ffffffff836c4abc>] l2tp_session_free+0x11c/0x200
[   21.850574]  RSP <ffff8801b5fdfc98>
[   21.854173] CR2: 0000000000000080
[   21.857674] ---[ end trace 0cfae96276948f2e ]---
[   21.862443] Kernel panic - not syncing: Fatal exception
[   21.868119] Dumping ftrace buffer:
[   21.871651]    (ftrace buffer empty)
[   21.875334] Kernel Offset: disabled
[   21.878954] Rebooting in 86400 seconds..