[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 14.598316] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 16.400003] random: sshd: uninitialized urandom read (32 bytes read) [ 16.813304] random: sshd: uninitialized urandom read (32 bytes read) [ 17.326013] random: sshd: uninitialized urandom read (32 bytes read) [ 17.472354] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.33' (ECDSA) to the list of known hosts. [ 22.947804] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 23.159348] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 23.167610] IP: [<ffffffff836c29cc>] l2tp_session_free+0x11c/0x200 [ 23.174052] PGD 1bdb15067 [ 23.176697] PUD 1bdb1a067 PMD 0 [ 23.180190] [ 23.181813] Oops: 0002 [#1] PREEMPT SMP KASAN [ 23.186282] Dumping ftrace buffer: [ 23.189795] (ftrace buffer empty) [ 23.193501] Modules linked in: [ 23.196792] CPU: 0 PID: 3798 Comm: syz-executor967 Not tainted 4.9.121-g681e57b #25 [ 23.204560] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 23.213910] task: ffff8801b68ab000 task.stack: ffff8801b58b0000 [ 23.219979] RIP: 0010:[<ffffffff836c29cc>] [<ffffffff836c29cc>] l2tp_session_free+0x11c/0x200 [ 23.228841] RSP: 0018:ffff8801b58b7ca0 EFLAGS: 00010246 [ 23.234275] RAX: dffffc0000000000 RBX: ffff8801b6a64f00 RCX: 0000000000000000 [ 23.241542] RDX: 1ffff10036d5a5c0 RSI: ffffffff836c29a1 RDI: ffff8801b6ad2e00 [ 23.248793] RBP: ffff8801b58b7cc0 R08: ffff8801b68ab8e8 R09: 0000000000000000 [ 23.256044] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b6ad2c80 [ 23.263291] R13: ffff8801b6a64f08 R14: 0000000000000000 R15: ffffffff83018be0 [ 23.270538] FS: 0000000001f19880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 23.278744] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 23.284611] CR2: 0000000000000080 CR3: 00000001bda4e000 CR4: 00000000001606f0 [ 23.291883] Stack: [ 23.294009] ffff8801d747d500 ffff8801b6a64f00 ffff8801d747d8d0 ffff8801d747d7d8 [ 23.302051] ffff8801b58b7ce8 ffffffff836ca2b2 ffff8801d747d940 ffff8801d747d500 [ 23.310080] ffffffff836ca1e0 ffff8801b58b7d20 ffffffff830260f5 ffff8801d747d940 [ 23.318097] Call Trace: [ 23.320678] [<ffffffff836ca2b2>] pppol2tp_session_destruct+0xd2/0x110 [ 23.327332] [<ffffffff836ca1e0>] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 23.333640] [<ffffffff830260f5>] __sk_destruct+0x55/0x590 [ 23.339244] [<ffffffff83018be0>] ? sock_release+0x1c0/0x1c0 [ 23.345031] [<ffffffff8302db83>] sk_destruct+0x63/0x80 [ 23.350383] [<ffffffff8302dbef>] __sk_free+0x4f/0x220 [ 23.355634] [<ffffffff8302ddeb>] sk_free+0x2b/0x40 [ 23.360640] [<ffffffff836cd5b9>] pppol2tp_release+0x239/0x2e0 [ 23.366589] [<ffffffff83018ab6>] sock_release+0x96/0x1c0 [ 23.372103] [<ffffffff83018bf6>] sock_close+0x16/0x20 [ 23.377357] [<ffffffff8157b403>] __fput+0x263/0x700 [ 23.382441] [<ffffffff8157b925>] ____fput+0x15/0x20 [ 23.387525] [<ffffffff8119a1fc>] task_work_run+0x10c/0x180 [ 23.393223] [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 [ 23.399540] [<ffffffff810064d4>] do_syscall_64+0x364/0x490 [ 23.405254] [<ffffffff839ffcd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 23.412166] 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 <f0> 41 ff 8e 80 00 00 00 74 69 e8 65 df c9 fd 4c 89 ea 48 b8 00 [ 23.439434] RIP [<ffffffff836c29cc>] l2tp_session_free+0x11c/0x200 [ 23.445961] RSP <ffff8801b58b7ca0> [ 23.449562] CR2: 0000000000000080 [ 23.453333] ---[ end trace d163e5ae1af620c7 ]--- [ 23.458104] Kernel panic - not syncing: Fatal exception [ 23.463807] Dumping ftrace buffer: [ 23.467333] (ftrace buffer empty) [ 23.471019] Kernel Offset: disabled [ 23.474622] Rebooting in 86400 seconds..