[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 15.590755] 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: [ 20.523232] random: sshd: uninitialized urandom read (32 bytes read) [ 20.797260] random: sshd: uninitialized urandom read (32 bytes read) [ 21.759313] random: sshd: uninitialized urandom read (32 bytes read) [ 21.896941] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.41' (ECDSA) to the list of known hosts. [ 27.406297] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 27.626205] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 27.634453] IP: [<ffffffff836bcd0c>] l2tp_session_free+0x11c/0x200 [ 27.640871] PGD 1c8e9d067 [ 27.643514] PUD 1b7af5067 PMD 0 [ 27.646995] [ 27.648617] Oops: 0002 [#1] PREEMPT SMP KASAN [ 27.653083] Dumping ftrace buffer: [ 27.656599] (ftrace buffer empty) [ 27.660288] Modules linked in: [ 27.663578] CPU: 1 PID: 3806 Comm: syz-executor963 Not tainted 4.9.113-g47bbcd6 #10 [ 27.671344] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.680671] task: ffff8801b6a78000 task.stack: ffff8801d9b70000 [ 27.686701] RIP: 0010:[<ffffffff836bcd0c>] [<ffffffff836bcd0c>] l2tp_session_free+0x11c/0x200 [ 27.695557] RSP: 0018:ffff8801d9b77ca0 EFLAGS: 00010246 [ 27.700991] RAX: dffffc0000000000 RBX: ffff8801cb068a00 RCX: 0000000000000000 [ 27.708236] RDX: 1ffff10036b4d6b0 RSI: ffffffff836bcce1 RDI: ffff8801b5a6b580 [ 27.715482] RBP: ffff8801d9b77cc0 R08: ffff8801b6a788e8 R09: 0000000000000000 [ 27.722730] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b5a6b400 [ 27.729976] R13: ffff8801cb068a08 R14: 0000000000000000 R15: ffffffff83013be0 [ 27.737225] FS: 0000000001449880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 27.745432] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 27.751295] CR2: 0000000000000080 CR3: 00000001bf25e000 CR4: 00000000001606f0 [ 27.758549] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 27.765794] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 27.773050] Stack: [ 27.775174] ffff8801b633ee80 ffff8801cb068a00 ffff8801b633f250 ffff8801b633f158 [ 27.783170] ffff8801d9b77ce8 ffffffff836c45f2 ffff8801b633f2c0 ffff8801b633ee80 [ 27.791167] ffffffff836c4520 ffff8801d9b77d20 ffffffff83021095 ffff8801b633f2c0 [ 27.799151] Call Trace: [ 27.801717] [<ffffffff836c45f2>] pppol2tp_session_destruct+0xd2/0x110 [ 27.808373] [<ffffffff836c4520>] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 27.814667] [<ffffffff83021095>] __sk_destruct+0x55/0x590 [ 27.820266] [<ffffffff83013be0>] ? sock_release+0x1c0/0x1c0 [ 27.826037] [<ffffffff83028b23>] sk_destruct+0x63/0x80 [ 27.831389] [<ffffffff83028b8f>] __sk_free+0x4f/0x220 [ 27.836638] [<ffffffff83028d8b>] sk_free+0x2b/0x40 [ 27.841629] [<ffffffff836c78f9>] pppol2tp_release+0x239/0x2e0 [ 27.847579] [<ffffffff83013ab6>] sock_release+0x96/0x1c0 [ 27.853090] [<ffffffff83013bf6>] sock_close+0x16/0x20 [ 27.858354] [<ffffffff815782e3>] __fput+0x263/0x700 [ 27.863435] [<ffffffff81578805>] ____fput+0x15/0x20 [ 27.868519] [<ffffffff8119838c>] task_work_run+0x10c/0x180 [ 27.874207] [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 [ 27.880509] [<ffffffff810064d4>] do_syscall_64+0x364/0x490 [ 27.886195] [<ffffffff839f9f93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 27.893092] 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 [ 27.919979] RIP [<ffffffff836bcd0c>] l2tp_session_free+0x11c/0x200 [ 27.926483] RSP <ffff8801d9b77ca0> [ 27.930081] CR2: 0000000000000080 [ 27.933587] ---[ end trace a2370ce780e2d6d7 ]--- [ 27.938346] Kernel panic - not syncing: Fatal exception [ 27.944179] Dumping ftrace buffer: [ 27.947694] (ftrace buffer empty) [ 27.951379] Kernel Offset: disabled [ 27.954979] Rebooting in 86400 seconds..