[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.228517] 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: [ 19.911057] random: sshd: uninitialized urandom read (32 bytes read) [ 20.331019] random: sshd: uninitialized urandom read (32 bytes read) [ 21.293055] random: sshd: uninitialized urandom read (32 bytes read) [ 30.244494] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.56' (ECDSA) to the list of known hosts. [ 35.697302] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 35.914387] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 35.922683] IP: [<ffffffff836be91c>] l2tp_session_free+0x11c/0x200 [ 35.929096] PGD 1cb259067 [ 35.931734] PUD 1cb25e067 PMD 0 [ 35.935214] [ 35.936832] Oops: 0002 [#1] PREEMPT SMP KASAN [ 35.941300] Dumping ftrace buffer: [ 35.944808] (ftrace buffer empty) [ 35.948491] Modules linked in: [ 35.951807] CPU: 0 PID: 3815 Comm: syz-executor827 Not tainted 4.9.116-g52be322 #17 [ 35.959573] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 35.968909] task: ffff8801b75e9800 task.stack: ffff8801d9168000 [ 35.974933] RIP: 0010:[<ffffffff836be91c>] [<ffffffff836be91c>] l2tp_session_free+0x11c/0x200 [ 35.983788] RSP: 0018:ffff8801d916fca0 EFLAGS: 00010246 [ 35.989217] RAX: dffffc0000000000 RBX: ffff8801cb3d7b80 RCX: 0000000000000000 [ 35.996461] RDX: 1ffff100394b8eb0 RSI: ffffffff836be8f1 RDI: ffff8801ca5c7580 [ 36.003712] RBP: ffff8801d916fcc0 R08: ffff8801b75ea0e8 R09: 0000000000000000 [ 36.010957] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801ca5c7400 [ 36.018199] R13: ffff8801cb3d7b88 R14: 0000000000000000 R15: ffffffff83014be0 [ 36.025445] FS: 00000000025d0880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 36.033642] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 36.039493] CR2: 0000000000000080 CR3: 00000001cb03c000 CR4: 00000000001606f0 [ 36.046733] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 36.053975] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 36.061217] Stack: [ 36.063342] ffff8801d9331100 ffff8801cb3d7b80 ffff8801d93314d0 ffff8801d93313d8 [ 36.071343] ffff8801d916fce8 ffffffff836c6202 ffff8801d9331540 ffff8801d9331100 [ 36.079848] ffffffff836c6130 ffff8801d916fd20 ffffffff83022095 ffff8801d9331540 [ 36.087841] Call Trace: [ 36.090410] [<ffffffff836c6202>] pppol2tp_session_destruct+0xd2/0x110 [ 36.097061] [<ffffffff836c6130>] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 36.103366] [<ffffffff83022095>] __sk_destruct+0x55/0x590 [ 36.108961] [<ffffffff83014be0>] ? sock_release+0x1c0/0x1c0 [ 36.114729] [<ffffffff83029b23>] sk_destruct+0x63/0x80 [ 36.120065] [<ffffffff83029b8f>] __sk_free+0x4f/0x220 [ 36.125315] [<ffffffff83029d8b>] sk_free+0x2b/0x40 [ 36.130304] [<ffffffff836c9509>] pppol2tp_release+0x239/0x2e0 [ 36.136250] [<ffffffff83014ab6>] sock_release+0x96/0x1c0 [ 36.141758] [<ffffffff83014bf6>] sock_close+0x16/0x20 [ 36.147007] [<ffffffff81578453>] __fput+0x263/0x700 [ 36.152083] [<ffffffff81578975>] ____fput+0x15/0x20 [ 36.157160] [<ffffffff8119838c>] task_work_run+0x10c/0x180 [ 36.162846] [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 [ 36.169146] [<ffffffff810064d4>] do_syscall_64+0x364/0x490 [ 36.174828] [<ffffffff839fbc13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 36.181723] 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 65 01 ca fd 4c 89 ea 48 b8 00 [ 36.208513] RIP [<ffffffff836be91c>] l2tp_session_free+0x11c/0x200 [ 36.215010] RSP <ffff8801d916fca0> [ 36.218606] CR2: 0000000000000080 [ 36.222222] ---[ end trace 5789cfe70567402b ]--- [ 36.226985] Kernel panic - not syncing: Fatal exception [ 36.232743] Dumping ftrace buffer: [ 36.236256] (ftrace buffer empty) [ 36.239943] Kernel Offset: disabled [ 36.243543] Rebooting in 86400 seconds..