[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 14.746666] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 27.289299] random: sshd: uninitialized urandom read (32 bytes read) [ 27.844800] random: sshd: uninitialized urandom read (32 bytes read) [ 28.369368] random: sshd: uninitialized urandom read (32 bytes read) [ 28.500809] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.23' (ECDSA) to the list of known hosts. [ 34.425945] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 34.625034] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 34.633416] IP: [] l2tp_session_free+0x11c/0x200 [ 34.639838] PGD 1bb61d067 [ 34.642479] PUD 1b8cec067 PMD 0 [ 34.645960] [ 34.647579] Oops: 0002 [#1] PREEMPT SMP KASAN [ 34.652291] Dumping ftrace buffer: [ 34.655819] (ftrace buffer empty) [ 34.659507] Modules linked in: [ 34.662795] CPU: 1 PID: 3810 Comm: syz-executor466 Not tainted 4.9.120-gf85543b #24 [ 34.670572] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 34.679902] task: ffff8801b6ae3000 task.stack: ffff8801b5690000 [ 34.686004] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 34.695100] RSP: 0018:ffff8801b5697ca0 EFLAGS: 00010246 [ 34.700563] RAX: dffffc0000000000 RBX: ffff8801b573e280 RCX: 0000000000000000 [ 34.707815] RDX: 1ffff10036c35f50 RSI: ffffffff836c29a1 RDI: ffff8801b61afa80 [ 34.715063] RBP: ffff8801b5697cc0 R08: ffff8801b6ae38e8 R09: 0000000000000000 [ 34.722312] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b61af900 [ 34.729657] R13: ffff8801b573e288 R14: 0000000000000000 R15: ffffffff83018be0 [ 34.736907] FS: 0000000001f09880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 34.745106] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 34.750966] CR2: 0000000000000080 CR3: 00000001ba3d2000 CR4: 00000000001606f0 [ 34.758365] Stack: [ 34.760557] ffff8801b57d2a80 ffff8801b573e280 ffff8801b57d2e50 ffff8801b57d2d58 [ 34.768572] ffff8801b5697ce8 ffffffff836ca2b2 ffff8801b57d2ec0 ffff8801b57d2a80 [ 34.776621] ffffffff836ca1e0 ffff8801b5697d20 ffffffff830260f5 ffff8801b57d2ec0 [ 34.784707] Call Trace: [ 34.787277] [] pppol2tp_session_destruct+0xd2/0x110 [ 34.793922] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 34.800222] [] __sk_destruct+0x55/0x590 [ 34.805827] [] ? sock_release+0x1c0/0x1c0 [ 34.811608] [] sk_destruct+0x63/0x80 [ 34.817081] [] __sk_free+0x4f/0x220 [ 34.822445] [] sk_free+0x2b/0x40 [ 34.827439] [] pppol2tp_release+0x239/0x2e0 [ 34.833396] [] sock_release+0x96/0x1c0 [ 34.838906] [] sock_close+0x16/0x20 [ 34.844157] [] __fput+0x263/0x700 [ 34.849250] [] ____fput+0x15/0x20 [ 34.854412] [] task_work_run+0x10c/0x180 [ 34.860203] [] exit_to_usermode_loop+0xfc/0x120 [ 34.860210] [] do_syscall_64+0x364/0x490 [ 34.860220] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 34.860341] 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 15 de c9 fd 4c 89 ea 48 b8 00 [ 34.860351] RIP [] l2tp_session_free+0x11c/0x200 [ 34.860354] RSP [ 34.860356] CR2: 0000000000000080 [ 34.860517] ---[ end trace 76ba84ddd34406a3 ]--- [ 34.860522] Kernel panic - not syncing: Fatal exception [ 34.866865] Dumping ftrace buffer: [ 34.866869] (ftrace buffer empty) [ 34.866871] Kernel Offset: disabled [ 34.932843] Rebooting in 86400 seconds..