[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.232290] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 18.828743] random: sshd: uninitialized urandom read (32 bytes read) [ 19.155794] random: sshd: uninitialized urandom read (32 bytes read) [ 20.151393] random: sshd: uninitialized urandom read (32 bytes read) [ 36.269769] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.30' (ECDSA) to the list of known hosts. [ 41.669509] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 41.874896] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 41.883120] IP: [] l2tp_session_free+0x11c/0x200 [ 41.889563] PGD 1c9d68067 [ 41.892205] PUD 1cb070067 PMD 0 [ 41.895700] [ 41.897368] Oops: 0002 [#1] PREEMPT SMP KASAN [ 41.901836] Dumping ftrace buffer: [ 41.905369] (ftrace buffer empty) [ 41.909095] Modules linked in: [ 41.912418] CPU: 0 PID: 3811 Comm: syz-executor960 Not tainted 4.9.113-g47bbcd6 #62 [ 41.920203] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 41.929558] task: ffff8801b71e6000 task.stack: ffff8801d98b0000 [ 41.935790] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 41.944697] RSP: 0018:ffff8801d98b7ca0 EFLAGS: 00010246 [ 41.950168] RAX: dffffc0000000000 RBX: ffff8801b76a7180 RCX: 0000000000000000 [ 41.957433] RDX: 1ffff100396f7570 RSI: ffffffff836bcce1 RDI: ffff8801cb7bab80 [ 41.964705] RBP: ffff8801d98b7cc0 R08: ffff8801b71e68e8 R09: 0000000000000000 [ 41.971974] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801cb7baa00 [ 41.979247] R13: ffff8801b76a7188 R14: 0000000000000000 R15: ffffffff83013be0 [ 41.986553] FS: 00000000021fe880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 41.994779] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 42.001093] CR2: 0000000000000080 CR3: 00000001c4eba000 CR4: 00000000001606f0 [ 42.008615] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 42.015873] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 42.023116] Stack: [ 42.025251] ffff8801d8bc3b80 ffff8801b76a7180 ffff8801d8bc3f50 ffff8801d8bc3e58 [ 42.033314] ffff8801d98b7ce8 ffffffff836c45f2 ffff8801d8bc3fc0 ffff8801d8bc3b80 [ 42.041321] ffffffff836c4520 ffff8801d98b7d20 ffffffff83021095 ffff8801d8bc3fc0 [ 42.049426] Call Trace: [ 42.052000] [] pppol2tp_session_destruct+0xd2/0x110 [ 42.058838] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 42.065148] [] __sk_destruct+0x55/0x590 [ 42.070766] [] ? sock_release+0x1c0/0x1c0 [ 42.076542] [] sk_destruct+0x63/0x80 [ 42.081888] [] __sk_free+0x4f/0x220 [ 42.087170] [] sk_free+0x2b/0x40 [ 42.093240] [] pppol2tp_release+0x239/0x2e0 [ 42.099192] [] sock_release+0x96/0x1c0 [ 42.104727] [] sock_close+0x16/0x20 [ 42.109987] [] __fput+0x263/0x700 [ 42.115073] [] ____fput+0x15/0x20 [ 42.120156] [] task_work_run+0x10c/0x180 [ 42.125853] [] exit_to_usermode_loop+0xfc/0x120 [ 42.132156] [] do_syscall_64+0x364/0x490 [ 42.137845] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 42.144752] 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 55 1d ca fd 4c 89 ea 48 b8 00 [ 42.171826] RIP [] l2tp_session_free+0x11c/0x200 [ 42.178333] RSP [ 42.181935] CR2: 0000000000000080 [ 42.185532] ---[ end trace a8b1fd8066ce5eb2 ]--- [ 42.190275] Kernel panic - not syncing: Fatal exception [ 42.196098] Dumping ftrace buffer: [ 42.199614] (ftrace buffer empty) [ 42.203301] Kernel Offset: disabled [ 42.206903] Rebooting in 86400 seconds..