[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 15.889976] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 17.125125] random: sshd: uninitialized urandom read (32 bytes read) [ 17.327756] random: sshd: uninitialized urandom read (32 bytes read) [ 18.376942] random: sshd: uninitialized urandom read (32 bytes read) [ 18.529848] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.61' (ECDSA) to the list of known hosts. [ 23.949026] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 24.138399] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 24.146644] IP: [] l2tp_session_free+0x11c/0x200 [ 24.153099] PGD 1cc5e6067 [ 24.155740] PUD 1c5344067 PMD 0 [ 24.159235] [ 24.160891] Oops: 0002 [#1] PREEMPT SMP KASAN [ 24.165363] Dumping ftrace buffer: [ 24.168877] (ftrace buffer empty) [ 24.172564] Modules linked in: [ 24.175868] CPU: 0 PID: 3798 Comm: syz-executor680 Not tainted 4.9.116-g0137ea2 #70 [ 24.183648] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 24.192988] task: ffff8801b6d2e000 task.stack: ffff8801b4cb0000 [ 24.199029] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 24.207877] RSP: 0018:ffff8801b4cb7ca0 EFLAGS: 00010246 [ 24.213314] RAX: dffffc0000000000 RBX: ffff8801caddec80 RCX: 0000000000000000 [ 24.220572] RDX: 1ffff100395bbf00 RSI: ffffffff836be8f1 RDI: ffff8801caddf800 [ 24.227819] RBP: ffff8801b4cb7cc0 R08: ffff8801b6d2e8e8 R09: 0000000000000000 [ 24.235067] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801caddf680 [ 24.242314] R13: ffff8801caddec88 R14: 0000000000000000 R15: ffffffff83014be0 [ 24.249592] FS: 00000000018d8880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 24.257816] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 24.263681] CR2: 0000000000000080 CR3: 00000001c3d75000 CR4: 00000000001606f0 [ 24.270945] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 24.278196] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 24.285442] Stack: [ 24.287574] ffff8801b575e600 ffff8801caddec80 ffff8801b575e9d0 ffff8801b575e8d8 [ 24.295578] ffff8801b4cb7ce8 ffffffff836c6202 ffff8801b575ea40 ffff8801b575e600 [ 24.303588] ffffffff836c6130 ffff8801b4cb7d20 ffffffff83022095 ffff8801b575ea40 [ 24.311634] Call Trace: [ 24.314221] [] pppol2tp_session_destruct+0xd2/0x110 [ 24.320877] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 24.327189] [] __sk_destruct+0x55/0x590 [ 24.332789] [] ? sock_release+0x1c0/0x1c0 [ 24.338563] [] sk_destruct+0x63/0x80 [ 24.343899] [] __sk_free+0x4f/0x220 [ 24.349149] [] sk_free+0x2b/0x40 [ 24.354144] [] pppol2tp_release+0x239/0x2e0 [ 24.360091] [] sock_release+0x96/0x1c0 [ 24.365607] [] sock_close+0x16/0x20 [ 24.370863] [] __fput+0x263/0x700 [ 24.375940] [] ____fput+0x15/0x20 [ 24.381046] [] task_work_run+0x10c/0x180 [ 24.386745] [] exit_to_usermode_loop+0xfc/0x120 [ 24.393052] [] do_syscall_64+0x364/0x490 [ 24.398752] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 24.405653] 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 65 01 ca fd 4c 89 ea 48 b8 00 [ 24.432665] RIP [] l2tp_session_free+0x11c/0x200 [ 24.439171] RSP [ 24.442775] CR2: 0000000000000080 [ 24.446330] ---[ end trace 9a6dff0db48e6518 ]--- [ 24.451099] Kernel panic - not syncing: Fatal exception [ 24.456799] Dumping ftrace buffer: [ 24.460317] (ftrace buffer empty) [ 24.464000] Kernel Offset: disabled [ 24.467629] Rebooting in 86400 seconds..