[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 15.453101] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 20.406786] random: sshd: uninitialized urandom read (32 bytes read) [ 20.747864] random: sshd: uninitialized urandom read (32 bytes read) [ 21.278668] random: sshd: uninitialized urandom read (32 bytes read) [ 34.820312] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.25' (ECDSA) to the list of known hosts. [ 40.385072] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 40.585321] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 40.593558] IP: [] l2tp_session_free+0x11c/0x200 [ 40.599984] PGD 1c1295067 [ 40.602625] PUD 1c129a067 PMD 0 [ 40.606113] [ 40.607735] Oops: 0002 [#1] PREEMPT SMP KASAN [ 40.612271] Dumping ftrace buffer: [ 40.615790] (ftrace buffer empty) [ 40.619475] Modules linked in: [ 40.622765] CPU: 1 PID: 3799 Comm: syz-executor687 Not tainted 4.9.122-g54068d6 #26 [ 40.630528] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 40.639857] task: ffff8801b8450000 task.stack: ffff8801b8440000 [ 40.645884] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 40.654734] RSP: 0018:ffff8801b8447ca0 EFLAGS: 00010246 [ 40.660240] RAX: dffffc0000000000 RBX: ffff8801cafc2280 RCX: 0000000000000000 [ 40.667490] RDX: 1ffff100371b2fa0 RSI: ffffffff836c39a1 RDI: ffff8801b8d97d00 [ 40.674791] RBP: ffff8801b8447cc0 R08: ffff8801b84508e8 R09: 0000000000000000 [ 40.682043] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b8d97b80 [ 40.689723] R13: ffff8801cafc2288 R14: 0000000000000000 R15: ffffffff83019be0 [ 40.696970] FS: 00000000015aa880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 40.705175] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 40.711030] CR2: 0000000000000080 CR3: 00000001b8996000 CR4: 00000000001606f0 [ 40.718325] Stack: [ 40.720457] ffff8801b8b25d80 ffff8801cafc2280 ffff8801b8b26150 ffff8801b8b26058 [ 40.728443] ffff8801b8447ce8 ffffffff836cb2b2 ffff8801b8b261c0 ffff8801b8b25d80 [ 40.736434] ffffffff836cb1e0 ffff8801b8447d20 ffffffff830270f5 ffff8801b8b261c0 [ 40.744436] Call Trace: [ 40.747003] [] pppol2tp_session_destruct+0xd2/0x110 [ 40.753650] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 40.759956] [] __sk_destruct+0x55/0x590 [ 40.765608] [] ? sock_release+0x1c0/0x1c0 [ 40.771402] [] sk_destruct+0x63/0x80 [ 40.776741] [] __sk_free+0x4f/0x220 [ 40.781996] [] sk_free+0x2b/0x40 [ 40.786995] [] pppol2tp_release+0x239/0x2e0 [ 40.792941] [] sock_release+0x96/0x1c0 [ 40.798453] [] sock_close+0x16/0x20 [ 40.803706] [] __fput+0x263/0x700 [ 40.808784] [] ____fput+0x15/0x20 [ 40.813862] [] task_work_run+0x10c/0x180 [ 40.819611] [] exit_to_usermode_loop+0xfc/0x120 [ 40.825911] [] do_syscall_64+0x364/0x490 [ 40.831603] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 40.838515] 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 41 ff 8e 80 00 00 00 74 69 e8 95 d3 c9 fd 4c 89 ea 48 b8 00 [ 40.865625] RIP [] l2tp_session_free+0x11c/0x200 [ 40.872156] RSP [ 40.875810] CR2: 0000000000000080 [ 40.879529] ---[ end trace 7b22990624b95fb1 ]--- [ 40.884267] Kernel panic - not syncing: Fatal exception [ 40.890036] Dumping ftrace buffer: [ 40.893555] (ftrace buffer empty) [ 40.897245] Kernel Offset: disabled [ 40.900867] Rebooting in 86400 seconds..