[....] 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[ 16.306847] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 20.199755] random: sshd: uninitialized urandom read (32 bytes read) [ 20.335697] random: sshd: uninitialized urandom read (32 bytes read) [ 20.840346] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.42' (ECDSA) to the list of known hosts. [ 26.372479] urandom_read: 1 callbacks suppressed [ 26.372483] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 26.600152] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 26.608497] IP: [] l2tp_session_free+0x11c/0x200 [ 26.614932] PGD 1c2624067 [ 26.617575] PUD 1c8c2f067 PMD 0 [ 26.621064] [ 26.622689] Oops: 0002 [#1] PREEMPT SMP KASAN [ 26.627161] Dumping ftrace buffer: [ 26.630716] (ftrace buffer empty) [ 26.634408] Modules linked in: [ 26.637704] CPU: 1 PID: 3787 Comm: syz-executor400 Not tainted 4.9.119-g9dc978d #23 [ 26.645518] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 26.654858] task: ffff8801bab1c800 task.stack: ffff8801b8da8000 [ 26.660890] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 26.669752] RSP: 0018:ffff8801b8dafca0 EFLAGS: 00010246 [ 26.675179] RAX: dffffc0000000000 RBX: ffff8801cafa2c80 RCX: 0000000000000000 [ 26.682546] RDX: 1ffff1003718b480 RSI: ffffffff836bf9a1 RDI: ffff8801b8c5a400 [ 26.689793] RBP: ffff8801b8dafcc0 R08: ffff8801bab1d0e8 R09: 0000000000000000 [ 26.697066] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b8c5a280 [ 26.704328] R13: ffff8801cafa2c88 R14: 0000000000000000 R15: ffffffff83015be0 [ 26.711701] FS: 0000000000e34880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 26.719919] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 26.725779] CR2: 0000000000000080 CR3: 00000001bc6db000 CR4: 00000000001606f0 [ 26.733036] Stack: [ 26.735158] ffff8801b9661100 ffff8801cafa2c80 ffff8801b96614d0 ffff8801b96613d8 [ 26.743254] ffff8801b8dafce8 ffffffff836c72b2 ffff8801b9661540 ffff8801b9661100 [ 26.751277] ffffffff836c71e0 ffff8801b8dafd20 ffffffff830230f5 ffff8801b9661540 [ 26.759295] Call Trace: [ 26.761896] [] pppol2tp_session_destruct+0xd2/0x110 [ 26.768711] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 26.775024] [] __sk_destruct+0x55/0x590 [ 26.780627] [] ? sock_release+0x1c0/0x1c0 [ 26.786405] [] sk_destruct+0x63/0x80 [ 26.791761] [] __sk_free+0x4f/0x220 [ 26.797020] [] sk_free+0x2b/0x40 [ 26.802025] [] pppol2tp_release+0x239/0x2e0 [ 26.808013] [] sock_release+0x96/0x1c0 [ 26.813531] [] sock_close+0x16/0x20 [ 26.818799] [] __fput+0x263/0x700 [ 26.823890] [] ____fput+0x15/0x20 [ 26.829000] [] task_work_run+0x10c/0x180 [ 26.834687] [] exit_to_usermode_loop+0xfc/0x120 [ 26.840987] [] do_syscall_64+0x364/0x490 [ 26.846680] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 26.853696] 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 f5 f0 c9 fd 4c 89 ea 48 b8 00 [ 26.881015] RIP [] l2tp_session_free+0x11c/0x200 [ 26.887537] RSP [ 26.891139] CR2: 0000000000000080 [ 26.894930] ---[ end trace 79a1810b8ec025d1 ]--- [ 26.899686] Kernel panic - not syncing: Fatal exception [ 26.905330] Dumping ftrace buffer: [ 26.908852] (ftrace buffer empty) [ 26.912537] Kernel Offset: disabled [ 26.916152] Rebooting in 86400 seconds..