[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.962225] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 22.054283] random: sshd: uninitialized urandom read (32 bytes read) [ 22.431587] random: sshd: uninitialized urandom read (32 bytes read) [ 22.936565] random: sshd: uninitialized urandom read (32 bytes read) [ 23.066301] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.24' (ECDSA) to the list of known hosts. [ 28.601313] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 28.808528] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 28.816778] IP: [] l2tp_session_free+0x11c/0x200 [ 28.823244] PGD 1ba9a3067 [ 28.825905] PUD 1ba983067 PMD 0 [ 28.829533] [ 28.831165] Oops: 0002 [#1] PREEMPT SMP KASAN [ 28.835665] Dumping ftrace buffer: [ 28.839193] (ftrace buffer empty) [ 28.843022] Modules linked in: [ 28.846351] CPU: 0 PID: 3805 Comm: syz-executor851 Not tainted 4.9.123-g8dd3fc2 #27 [ 28.854144] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 28.863500] task: ffff8801bab76000 task.stack: ffff8801b6e88000 [ 28.869551] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 28.878427] RSP: 0018:ffff8801b6e8fca0 EFLAGS: 00010246 [ 28.883867] RAX: dffffc0000000000 RBX: ffff8801b6fed180 RCX: 0000000000000000 [ 28.891135] RDX: 1ffff10036de10d0 RSI: ffffffff836c4991 RDI: ffff8801b6f08680 [ 28.898396] RBP: ffff8801b6e8fcc0 R08: ffff8801bab768e8 R09: 0000000000000000 [ 28.905662] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b6f08500 [ 28.912977] R13: ffff8801b6fed188 R14: 0000000000000000 R15: ffffffff8301abe0 [ 28.920251] FS: 00000000011bb880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 28.928572] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 28.934440] CR2: 0000000000000080 CR3: 00000001ba915000 CR4: 00000000001606f0 [ 28.941697] Stack: [ 28.943828] ffff8801b6f22a80 ffff8801b6fed180 ffff8801b6f22e50 ffff8801b6f22d58 [ 28.952005] ffff8801b6e8fce8 ffffffff836cc2a2 ffff8801b6f22ec0 ffff8801b6f22a80 [ 28.960151] ffffffff836cc1d0 ffff8801b6e8fd20 ffffffff830280f5 ffff8801b6f22ec0 [ 28.968163] Call Trace: [ 28.970735] [] pppol2tp_session_destruct+0xd2/0x110 [ 28.977569] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 28.983882] [] __sk_destruct+0x55/0x590 [ 28.989495] [] ? sock_release+0x1c0/0x1c0 [ 28.995289] [] sk_destruct+0x63/0x80 [ 29.000647] [] __sk_free+0x4f/0x220 [ 29.005911] [] sk_free+0x2b/0x40 [ 29.010914] [] pppol2tp_release+0x239/0x2e0 [ 29.016882] [] sock_release+0x96/0x1c0 [ 29.022518] [] sock_close+0x16/0x20 [ 29.027784] [] __fput+0x263/0x700 [ 29.032880] [] ____fput+0x15/0x20 [ 29.037964] [] task_work_run+0x10c/0x180 [ 29.043658] [] exit_to_usermode_loop+0xfc/0x120 [ 29.049960] [] do_syscall_64+0x364/0x490 [ 29.055655] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 29.062562] 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 [ 29.090027] RIP [] l2tp_session_free+0x11c/0x200 [ 29.096540] RSP [ 29.100209] CR2: 0000000000000080 [ 29.103947] ---[ end trace 90b2a75c962155b1 ]--- [ 29.108732] Kernel panic - not syncing: Fatal exception [ 29.114476] Dumping ftrace buffer: [ 29.118059] (ftrace buffer empty) [ 29.121757] Kernel Offset: disabled [ 29.125367] Rebooting in 86400 seconds..