[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 12.901928] 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: [ 16.835314] random: sshd: uninitialized urandom read (32 bytes read) [ 17.223988] random: sshd: uninitialized urandom read (32 bytes read) [ 17.706602] random: sshd: uninitialized urandom read (32 bytes read) [ 17.846169] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.54' (ECDSA) to the list of known hosts. [ 23.332994] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 23.549117] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 23.557417] IP: [<ffffffff836bf9cc>] l2tp_session_free+0x11c/0x200 [ 23.563896] PGD 1cb451067 [ 23.566553] PUD 1cb443067 PMD 0 [ 23.570055] [ 23.571686] Oops: 0002 [#1] PREEMPT SMP KASAN [ 23.576165] Dumping ftrace buffer: [ 23.579769] (ftrace buffer empty) [ 23.583471] Modules linked in: [ 23.586757] CPU: 0 PID: 3804 Comm: syz-executor250 Not tainted 4.9.119-g92e8704 #74 [ 23.594526] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 23.603863] task: ffff8801b757c800 task.stack: ffff8801b5a98000 [ 23.609895] RIP: 0010:[<ffffffff836bf9cc>] [<ffffffff836bf9cc>] l2tp_session_free+0x11c/0x200 [ 23.618755] RSP: 0018:ffff8801b5a9fca0 EFLAGS: 00010246 [ 23.624288] RAX: dffffc0000000000 RBX: ffff8801b6502c80 RCX: 0000000000000000 [ 23.631537] RDX: 1ffff10036e6f080 RSI: ffffffff836bf9a1 RDI: ffff8801b7378400 [ 23.638789] RBP: ffff8801b5a9fcc0 R08: ffff8801b757d0e8 R09: 0000000000000000 [ 23.646042] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b7378280 [ 23.653291] R13: ffff8801b6502c88 R14: 0000000000000000 R15: ffffffff83015be0 [ 23.660538] FS: 0000000000733880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 23.668744] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 23.674609] CR2: 0000000000000080 CR3: 00000001c44e8000 CR4: 00000000001606f0 [ 23.681863] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 23.689189] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 23.696526] Stack: [ 23.698663] ffff8801b5a64c80 ffff8801b6502c80 ffff8801b5a65050 ffff8801b5a64f58 [ 23.706661] ffff8801b5a9fce8 ffffffff836c72b2 ffff8801b5a650c0 ffff8801b5a64c80 [ 23.714795] ffffffff836c71e0 ffff8801b5a9fd20 ffffffff830230f5 ffff8801b5a650c0 [ 23.722856] Call Trace: [ 23.725435] [<ffffffff836c72b2>] pppol2tp_session_destruct+0xd2/0x110 [ 23.732280] [<ffffffff836c71e0>] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 23.738581] [<ffffffff830230f5>] __sk_destruct+0x55/0x590 [ 23.744253] [<ffffffff83015be0>] ? sock_release+0x1c0/0x1c0 [ 23.750046] [<ffffffff8302ab83>] sk_destruct+0x63/0x80 [ 23.755444] [<ffffffff8302abef>] __sk_free+0x4f/0x220 [ 23.760708] [<ffffffff8302adeb>] sk_free+0x2b/0x40 [ 23.765705] [<ffffffff836ca5b9>] pppol2tp_release+0x239/0x2e0 [ 23.771656] [<ffffffff83015ab6>] sock_release+0x96/0x1c0 [ 23.777170] [<ffffffff83015bf6>] sock_close+0x16/0x20 [ 23.782472] [<ffffffff81578693>] __fput+0x263/0x700 [ 23.787559] [<ffffffff81578bb5>] ____fput+0x15/0x20 [ 23.792641] [<ffffffff8119838c>] task_work_run+0x10c/0x180 [ 23.798329] [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 [ 23.804623] [<ffffffff810064d4>] do_syscall_64+0x364/0x490 [ 23.810311] [<ffffffff839fccd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 23.817206] 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 f5 f0 c9 fd 4c 89 ea 48 b8 00 [ 23.844621] RIP [<ffffffff836bf9cc>] l2tp_session_free+0x11c/0x200 [ 23.851132] RSP <ffff8801b5a9fca0> [ 23.854744] CR2: 0000000000000080 [ 23.858257] ---[ end trace f73d6bd8e14b78d3 ]--- [ 23.863033] Kernel panic - not syncing: Fatal exception [ 23.868730] Dumping ftrace buffer: [ 23.872246] (ftrace buffer empty) [ 23.875931] Kernel Offset: disabled [ 23.879537] Rebooting in 86400 seconds..