[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 16.854886] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 28.516918] random: sshd: uninitialized urandom read (32 bytes read) [ 28.805890] random: sshd: uninitialized urandom read (32 bytes read) [ 29.212840] random: sshd: uninitialized urandom read (32 bytes read) [ 41.316727] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.61' (ECDSA) to the list of known hosts. [ 46.811831] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 47.034735] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 47.043094] IP: [] l2tp_session_free+0x11c/0x200 [ 47.049860] PGD 1b64af067 [ 47.052533] PUD 1baffa067 PMD 0 [ 47.056084] [ 47.057726] Oops: 0002 [#1] PREEMPT SMP KASAN [ 47.062232] Dumping ftrace buffer: [ 47.062236] (ftrace buffer empty) [ 47.062240] Modules linked in: [ 47.062249] CPU: 0 PID: 3808 Comm: syz-executor817 Not tainted 4.9.120-gf85543b #24 [ 47.062253] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 47.062259] task: ffff8801b830b000 task.stack: ffff8801d9738000 [ 47.062276] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 47.062280] RSP: 0018:ffff8801d973fca0 EFLAGS: 00010246 [ 47.062288] RAX: dffffc0000000000 RBX: ffff8801b6ee6000 RCX: 0000000000000000 [ 47.062292] RDX: 1ffff10036ddcd20 RSI: ffffffff836c29a1 RDI: ffff8801b6ee6900 [ 47.062296] RBP: ffff8801d973fcc0 R08: ffff8801b830b8e8 R09: 0000000000000000 [ 47.062299] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b6ee6780 [ 47.062303] R13: ffff8801b6ee6008 R14: 0000000000000000 R15: ffffffff83018be0 [ 47.062309] FS: 0000000000dac880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 47.062313] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 47.062317] CR2: 0000000000000080 CR3: 00000001b816e000 CR4: 00000000001606f0 [ 47.062325] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 47.062329] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 47.062330] Stack: [ 47.062342] ffff8801d97b1980 ffff8801b6ee6000 ffff8801d97b1d50 ffff8801d97b1c58 [ 47.062352] ffff8801d973fce8 ffffffff836ca2b2 ffff8801d97b1dc0 ffff8801d97b1980 [ 47.062362] ffffffff836ca1e0 ffff8801d973fd20 ffffffff830260f5 ffff8801d97b1dc0 [ 47.062364] Call Trace: [ 47.062375] [] pppol2tp_session_destruct+0xd2/0x110 [ 47.062382] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 47.062391] [] __sk_destruct+0x55/0x590 [ 47.062400] [] ? sock_release+0x1c0/0x1c0 [ 47.062407] [] sk_destruct+0x63/0x80 [ 47.062414] [] __sk_free+0x4f/0x220 [ 47.062421] [] sk_free+0x2b/0x40 [ 47.062428] [] pppol2tp_release+0x239/0x2e0 [ 47.062436] [] sock_release+0x96/0x1c0 [ 47.062443] [] sock_close+0x16/0x20 [ 47.062453] [] __fput+0x263/0x700 [ 47.062461] [] ____fput+0x15/0x20 [ 47.062470] [] task_work_run+0x10c/0x180 [ 47.062481] [] exit_to_usermode_loop+0xfc/0x120 [ 47.062488] [] do_syscall_64+0x364/0x490 [ 47.062498] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 47.062617] 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 [ 47.062625] RIP [] l2tp_session_free+0x11c/0x200 [ 47.062628] RSP [ 47.062631] CR2: 0000000000000080 [ 47.064394] ---[ end trace c2922d312eab5ed6 ]--- [ 47.064399] Kernel panic - not syncing: Fatal exception [ 47.066550] Dumping ftrace buffer: [ 47.066553] (ftrace buffer empty) [ 47.066568] Kernel Offset: disabled [ 47.359453] Rebooting in 86400 seconds..