[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.076581] 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: [ 14.941414] random: sshd: uninitialized urandom read (32 bytes read) [ 15.124367] random: sshd: uninitialized urandom read (32 bytes read) [ 16.094394] random: sshd: uninitialized urandom read (32 bytes read) [ 16.230985] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.38' (ECDSA) to the list of known hosts. [ 21.645389] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 21.842083] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 21.850310] IP: [<ffffffff836bcd0c>] l2tp_session_free+0x11c/0x200 [ 21.856732] PGD 1bda2b067 [ 21.859373] PUD 1bda80067 PMD 0 [ 21.862857] [ 21.864475] Oops: 0002 [#1] PREEMPT SMP KASAN [ 21.868943] Dumping ftrace buffer: [ 21.872456] (ftrace buffer empty) [ 21.876145] Modules linked in: [ 21.879430] CPU: 0 PID: 3797 Comm: syz-executor517 Not tainted 4.9.113-g47bbcd6 #10 [ 21.887193] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 21.896521] task: ffff8801b7953000 task.stack: ffff8801b5588000 [ 21.902583] RIP: 0010:[<ffffffff836bcd0c>] [<ffffffff836bcd0c>] l2tp_session_free+0x11c/0x200 [ 21.911443] RSP: 0018:ffff8801b558fca0 EFLAGS: 00010246 [ 21.916865] RAX: dffffc0000000000 RBX: ffff8801b556c780 RCX: 0000000000000000 [ 21.924114] RDX: 1ffff10036ce8c30 RSI: ffffffff836bcce1 RDI: ffff8801b6746180 [ 21.931361] RBP: ffff8801b558fcc0 R08: ffff8801b79538e8 R09: 0000000000000000 [ 21.938605] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b6746000 [ 21.945848] R13: ffff8801b556c788 R14: 0000000000000000 R15: ffffffff83013be0 [ 21.953093] FS: 000000000195e880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 21.961292] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 21.967144] CR2: 0000000000000080 CR3: 00000001b9e22000 CR4: 00000000001606f0 [ 21.974390] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 21.981633] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 21.988881] Stack: [ 21.991010] ffff8801b5a0f700 ffff8801b556c780 ffff8801b5a0fad0 ffff8801b5a0f9d8 [ 21.999014] ffff8801b558fce8 ffffffff836c45f2 ffff8801b5a0fb40 ffff8801b5a0f700 [ 22.007005] ffffffff836c4520 ffff8801b558fd20 ffffffff83021095 ffff8801b5a0fb40 [ 22.014986] Call Trace: [ 22.017554] [<ffffffff836c45f2>] pppol2tp_session_destruct+0xd2/0x110 [ 22.024198] [<ffffffff836c4520>] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 22.030504] [<ffffffff83021095>] __sk_destruct+0x55/0x590 [ 22.036105] [<ffffffff83013be0>] ? sock_release+0x1c0/0x1c0 [ 22.041880] [<ffffffff83028b23>] sk_destruct+0x63/0x80 [ 22.047226] [<ffffffff83028b8f>] __sk_free+0x4f/0x220 [ 22.052476] [<ffffffff83028d8b>] sk_free+0x2b/0x40 [ 22.057485] [<ffffffff836c78f9>] pppol2tp_release+0x239/0x2e0 [ 22.063432] [<ffffffff83013ab6>] sock_release+0x96/0x1c0 [ 22.068942] [<ffffffff83013bf6>] sock_close+0x16/0x20 [ 22.074197] [<ffffffff815782e3>] __fput+0x263/0x700 [ 22.079281] [<ffffffff81578805>] ____fput+0x15/0x20 [ 22.084362] [<ffffffff8119838c>] task_work_run+0x10c/0x180 [ 22.090067] [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 [ 22.096366] [<ffffffff810064d4>] do_syscall_64+0x364/0x490 [ 22.102051] [<ffffffff839f9f93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 22.109699] 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 1d ca fd 4c 89 ea 48 b8 00 [ 22.136521] RIP [<ffffffff836bcd0c>] l2tp_session_free+0x11c/0x200 [ 22.143024] RSP <ffff8801b558fca0> [ 22.146620] CR2: 0000000000000080 [ 22.150325] ---[ end trace ed12a63ae7f41a4c ]--- [ 22.155079] Kernel panic - not syncing: Fatal exception [ 22.160905] Dumping ftrace buffer: [ 22.164424] (ftrace buffer empty) [ 22.168109] Kernel Offset: disabled [ 22.171707] Rebooting in 86400 seconds..