[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 12.204642] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 17.463454] random: sshd: uninitialized urandom read (32 bytes read) [ 17.663168] random: sshd: uninitialized urandom read (32 bytes read) [ 18.108526] random: sshd: uninitialized urandom read (32 bytes read) [ 51.955039] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.12' (ECDSA) to the list of known hosts. [ 57.404938] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 57.571285] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 57.579513] IP: [] l2tp_session_free+0x11c/0x200 [ 57.585934] PGD 1bc765067 [ 57.588574] PUD 1bc51b067 PMD 0 [ 57.592053] [ 57.593670] Oops: 0002 [#1] PREEMPT SMP KASAN [ 57.598137] Dumping ftrace buffer: [ 57.601691] (ftrace buffer empty) [ 57.605389] Modules linked in: [ 57.608673] CPU: 1 PID: 3778 Comm: syz-executor818 Not tainted 4.9.117-g8b21e85 #19 [ 57.616456] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 57.625791] task: ffff8801bd8c1800 task.stack: ffff8801d9888000 [ 57.631817] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 57.640660] RSP: 0018:ffff8801d988fca0 EFLAGS: 00010246 [ 57.646079] RAX: dffffc0000000000 RBX: ffff8801bc711b80 RCX: 0000000000000000 [ 57.653321] RDX: 1ffff1003784fc80 RSI: ffffffff836bf8f1 RDI: ffff8801bc27e400 [ 57.660570] RBP: ffff8801d988fcc0 R08: ffff8801bd8c20e8 R09: 0000000000000000 [ 57.667815] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801bc27e280 [ 57.675069] R13: ffff8801bc711b88 R14: 0000000000000000 R15: ffffffff83015be0 [ 57.682334] FS: 0000000001c98880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 57.690539] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 57.696390] CR2: 0000000000000080 CR3: 00000001bc62e000 CR4: 00000000001606f0 [ 57.703633] Stack: [ 57.705756] ffff8801d9ba0000 ffff8801bc711b80 ffff8801d9ba03d0 ffff8801d9ba02d8 [ 57.713744] ffff8801d988fce8 ffffffff836c7202 ffff8801d9ba0440 ffff8801d9ba0000 [ 57.721736] ffffffff836c7130 ffff8801d988fd20 ffffffff83023095 ffff8801d9ba0440 [ 57.729714] Call Trace: [ 57.732275] [] pppol2tp_session_destruct+0xd2/0x110 [ 57.738917] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 57.745211] [] __sk_destruct+0x55/0x590 [ 57.750804] [] ? sock_release+0x1c0/0x1c0 [ 57.756658] [] sk_destruct+0x63/0x80 [ 57.762005] [] __sk_free+0x4f/0x220 [ 57.767257] [] sk_free+0x2b/0x40 [ 57.772242] [] pppol2tp_release+0x239/0x2e0 [ 57.778189] [] sock_release+0x96/0x1c0 [ 57.783723] [] sock_close+0x16/0x20 [ 57.788972] [] __fput+0x263/0x700 [ 57.794045] [] ____fput+0x15/0x20 [ 57.799122] [] task_work_run+0x10c/0x180 [ 57.804821] [] exit_to_usermode_loop+0xfc/0x120 [ 57.811120] [] do_syscall_64+0x364/0x490 [ 57.816802] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 57.823709] 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 e5 f1 c9 fd 4c 89 ea 48 b8 00 [ 57.850407] RIP [] l2tp_session_free+0x11c/0x200 [ 57.856923] RSP [ 57.860520] CR2: 0000000000000080 [ 57.865302] ---[ end trace 77fa6c0f65c1bb88 ]--- [ 57.870052] Kernel panic - not syncing: Fatal exception [ 57.875708] Dumping ftrace buffer: [ 57.879225] (ftrace buffer empty) [ 57.882909] Kernel Offset: disabled [ 57.886510] Rebooting in 86400 seconds..