[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 15.996433] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 17.600742] random: sshd: uninitialized urandom read (32 bytes read) [ 17.831273] random: sshd: uninitialized urandom read (32 bytes read) [ 18.359586] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.15.192' (ECDSA) to the list of known hosts. [ 24.193234] urandom_read: 1 callbacks suppressed [ 24.193237] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 24.412575] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 24.420809] IP: [] l2tp_session_free+0x11c/0x200 [ 24.427249] PGD 1ca5ac067 [ 24.429888] PUD 1cb02a067 PMD 0 [ 24.433388] [ 24.435010] Oops: 0002 [#1] PREEMPT SMP KASAN [ 24.439482] Dumping ftrace buffer: [ 24.442996] (ftrace buffer empty) [ 24.446684] Modules linked in: [ 24.449975] CPU: 0 PID: 3795 Comm: syz-executor904 Not tainted 4.9.123-g8dd3fc2 #27 [ 24.457742] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 24.467070] task: ffff8801b8d43000 task.stack: ffff8801b65c0000 [ 24.473121] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 24.482020] RSP: 0018:ffff8801b65c7ca0 EFLAGS: 00010246 [ 24.487445] RAX: dffffc0000000000 RBX: ffff8801b6732c80 RCX: 0000000000000000 [ 24.494693] RDX: 1ffff10036cfb880 RSI: ffffffff836c4991 RDI: ffff8801b67dc400 [ 24.501940] RBP: ffff8801b65c7cc0 R08: ffff8801b8d438e8 R09: 0000000000000000 [ 24.509206] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b67dc280 [ 24.516471] R13: ffff8801b6732c88 R14: 0000000000000000 R15: ffffffff8301abe0 [ 24.523717] FS: 0000000000e06880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 24.531916] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 24.537794] CR2: 0000000000000080 CR3: 00000001c8e12000 CR4: 00000000001606f0 [ 24.545052] Stack: [ 24.547176] ffff8801b6a86600 ffff8801b6732c80 ffff8801b6a869d0 ffff8801b6a868d8 [ 24.555203] ffff8801b65c7ce8 ffffffff836cc2a2 ffff8801b6a86a40 ffff8801b6a86600 [ 24.563191] ffffffff836cc1d0 ffff8801b65c7d20 ffffffff830280f5 ffff8801b6a86a40 [ 24.571195] Call Trace: [ 24.573776] [] pppol2tp_session_destruct+0xd2/0x110 [ 24.580422] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 24.586715] [] __sk_destruct+0x55/0x590 [ 24.592333] [] ? sock_release+0x1c0/0x1c0 [ 24.598130] [] sk_destruct+0x63/0x80 [ 24.603482] [] __sk_free+0x4f/0x220 [ 24.608754] [] sk_free+0x2b/0x40 [ 24.613765] [] pppol2tp_release+0x239/0x2e0 [ 24.619722] [] sock_release+0x96/0x1c0 [ 24.625247] [] sock_close+0x16/0x20 [ 24.630499] [] __fput+0x263/0x700 [ 24.635590] [] ____fput+0x15/0x20 [ 24.640684] [] task_work_run+0x10c/0x180 [ 24.646383] [] exit_to_usermode_loop+0xfc/0x120 [ 24.652707] [] do_syscall_64+0x364/0x490 [ 24.658414] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 24.665340] 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 c3 c9 fd 4c 89 ea 48 b8 00 [ 24.692717] RIP [] l2tp_session_free+0x11c/0x200 [ 24.699225] RSP [ 24.702824] CR2: 0000000000000080 [ 24.706564] ---[ end trace 7f874424c0c6384c ]--- [ 24.711314] Kernel panic - not syncing: Fatal exception [ 24.716944] Dumping ftrace buffer: [ 24.720469] (ftrace buffer empty) [ 24.724152] Kernel Offset: disabled [ 24.727771] Rebooting in 86400 seconds..