[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.177945] 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: [ 15.071403] random: sshd: uninitialized urandom read (32 bytes read) [ 15.287298] random: sshd: uninitialized urandom read (32 bytes read) [ 16.163362] random: sshd: uninitialized urandom read (32 bytes read) [ 16.292371] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.39' (ECDSA) to the list of known hosts. [ 21.698706] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 21.894877] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 21.903118] IP: [<ffffffff836bcf0c>] l2tp_session_free+0x11c/0x200 [ 21.909549] PGD 1c713b067 [ 21.912193] PUD 1c8241067 PMD 0 [ 21.915696] [ 21.917316] Oops: 0002 [#1] PREEMPT SMP KASAN [ 21.921783] Dumping ftrace buffer: [ 21.925294] (ftrace buffer empty) [ 21.929066] Modules linked in: [ 21.932358] CPU: 1 PID: 3791 Comm: syz-executor494 Not tainted 4.9.113-g8956c50 #15 [ 21.940124] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 21.949454] task: ffff8801b8971800 task.stack: ffff8801d90d0000 [ 21.955506] RIP: 0010:[<ffffffff836bcf0c>] [<ffffffff836bcf0c>] l2tp_session_free+0x11c/0x200 [ 21.964354] RSP: 0018:ffff8801d90d7ca0 EFLAGS: 00010246 [ 21.969775] RAX: dffffc0000000000 RBX: ffff8801b8629680 RCX: 0000000000000000 [ 21.977022] RDX: 1ffff10036d80570 RSI: ffffffff836bcee1 RDI: ffff8801b6c02b80 [ 21.984281] RBP: ffff8801d90d7cc0 R08: ffff8801b89720e8 R09: 0000000000000000 [ 21.991530] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b6c02a00 [ 21.998776] R13: ffff8801b8629688 R14: 0000000000000000 R15: ffffffff83013be0 [ 22.006037] FS: 0000000002179880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 22.014245] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 22.020274] CR2: 0000000000000080 CR3: 00000001bd523000 CR4: 00000000001606f0 [ 22.027528] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 22.034776] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 22.042026] Stack: [ 22.044165] ffff8801b6993300 ffff8801b8629680 ffff8801b69936d0 ffff8801b69935d8 [ 22.052194] ffff8801d90d7ce8 ffffffff836c47f2 ffff8801b6993740 ffff8801b6993300 [ 22.060204] ffffffff836c4720 ffff8801d90d7d20 ffffffff83021095 ffff8801b6993740 [ 22.068203] Call Trace: [ 22.070768] [<ffffffff836c47f2>] pppol2tp_session_destruct+0xd2/0x110 [ 22.077419] [<ffffffff836c4720>] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 22.083710] [<ffffffff83021095>] __sk_destruct+0x55/0x590 [ 22.089318] [<ffffffff83013be0>] ? sock_release+0x1c0/0x1c0 [ 22.095091] [<ffffffff83028b23>] sk_destruct+0x63/0x80 [ 22.100426] [<ffffffff83028b8f>] __sk_free+0x4f/0x220 [ 22.105675] [<ffffffff83028d8b>] sk_free+0x2b/0x40 [ 22.110662] [<ffffffff836c7af9>] pppol2tp_release+0x239/0x2e0 [ 22.116617] [<ffffffff83013ab6>] sock_release+0x96/0x1c0 [ 22.122137] [<ffffffff83013bf6>] sock_close+0x16/0x20 [ 22.127388] [<ffffffff815782e3>] __fput+0x263/0x700 [ 22.132467] [<ffffffff81578805>] ____fput+0x15/0x20 [ 22.137548] [<ffffffff8119838c>] task_work_run+0x10c/0x180 [ 22.143239] [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 [ 22.149533] [<ffffffff810064d4>] do_syscall_64+0x364/0x490 [ 22.155217] [<ffffffff839fa193>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 22.162112] 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 1b ca fd 4c 89 ea 48 b8 00 [ 22.189085] RIP [<ffffffff836bcf0c>] l2tp_session_free+0x11c/0x200 [ 22.195596] RSP <ffff8801d90d7ca0> [ 22.199201] CR2: 0000000000000080 [ 22.203057] ---[ end trace 2b8b88e5cf1633b9 ]--- [ 22.207820] Kernel panic - not syncing: Fatal exception [ 22.213610] Dumping ftrace buffer: [ 22.217129] (ftrace buffer empty) [ 22.220811] Kernel Offset: disabled [ 22.224408] Rebooting in 86400 seconds..