[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 15.710883] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 24.145885] random: sshd: uninitialized urandom read (32 bytes read) [ 24.543897] random: sshd: uninitialized urandom read (32 bytes read) [ 25.464760] random: sshd: uninitialized urandom read (32 bytes read) [ 34.452266] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.42' (ECDSA) to the list of known hosts. [ 39.834064] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 40.058566] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 40.066859] IP: [] l2tp_session_free+0x11c/0x200 [ 40.073295] PGD 1bbe1f067 [ 40.075938] PUD 1cb0a2067 PMD 0 [ 40.079419] [ 40.081159] Oops: 0002 [#1] PREEMPT SMP KASAN [ 40.085661] Dumping ftrace buffer: [ 40.089191] (ftrace buffer empty) [ 40.092882] Modules linked in: [ 40.096184] CPU: 1 PID: 3809 Comm: syz-executor534 Not tainted 4.9.113-g47bbcd6 #62 [ 40.103974] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 40.113317] task: ffff8801d9544800 task.stack: ffff8801d9100000 [ 40.119435] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 40.128288] RSP: 0018:ffff8801d9107ca0 EFLAGS: 00010246 [ 40.133710] RAX: dffffc0000000000 RBX: ffff8801b605ac80 RCX: 0000000000000000 [ 40.140951] RDX: 1ffff10036e86920 RSI: ffffffff836bcce1 RDI: ffff8801b7434900 [ 40.148214] RBP: ffff8801d9107cc0 R08: ffff8801d95450e8 R09: 0000000000000000 [ 40.155472] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b7434780 [ 40.162724] R13: ffff8801b605ac88 R14: 0000000000000000 R15: ffffffff83013be0 [ 40.169969] FS: 000000000258b880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 40.178188] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 40.184043] CR2: 0000000000000080 CR3: 00000001bd2b3000 CR4: 00000000001606f0 [ 40.191328] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 40.198748] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 40.205999] Stack: [ 40.208125] ffff8801c572e600 ffff8801b605ac80 ffff8801c572e9d0 ffff8801c572e8d8 [ 40.216133] ffff8801d9107ce8 ffffffff836c45f2 ffff8801c572ea40 ffff8801c572e600 [ 40.224151] ffffffff836c4520 ffff8801d9107d20 ffffffff83021095 ffff8801c572ea40 [ 40.232134] Call Trace: [ 40.234708] [] pppol2tp_session_destruct+0xd2/0x110 [ 40.241452] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 40.247927] [] __sk_destruct+0x55/0x590 [ 40.253537] [] ? sock_release+0x1c0/0x1c0 [ 40.259312] [] sk_destruct+0x63/0x80 [ 40.264649] [] __sk_free+0x4f/0x220 [ 40.269899] [] sk_free+0x2b/0x40 [ 40.274988] [] pppol2tp_release+0x239/0x2e0 [ 40.280949] [] sock_release+0x96/0x1c0 [ 40.286472] [] sock_close+0x16/0x20 [ 40.291725] [] __fput+0x263/0x700 [ 40.296802] [] ____fput+0x15/0x20 [ 40.302056] [] task_work_run+0x10c/0x180 [ 40.307744] [] exit_to_usermode_loop+0xfc/0x120 [ 40.314036] [] do_syscall_64+0x364/0x490 [ 40.319814] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 40.326713] 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 55 1d ca fd 4c 89 ea 48 b8 00 [ 40.353900] RIP [] l2tp_session_free+0x11c/0x200 [ 40.360477] RSP [ 40.364077] CR2: 0000000000000080 [ 40.367649] ---[ end trace a83bff7047d5ea15 ]--- [ 40.372594] Kernel panic - not syncing: Fatal exception [ 40.378598] Dumping ftrace buffer: [ 40.382125] (ftrace buffer empty) [ 40.385815] Kernel Offset: disabled [ 40.389529] Rebooting in 86400 seconds..