[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.495452] 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: [ 18.868751] random: sshd: uninitialized urandom read (32 bytes read) [ 19.233994] random: sshd: uninitialized urandom read (32 bytes read) [ 19.749426] random: sshd: uninitialized urandom read (32 bytes read) [ 19.903240] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.45' (ECDSA) to the list of known hosts. [ 25.574035] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 25.780142] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 25.788366] IP: [<ffffffff836bf9cc>] l2tp_session_free+0x11c/0x200 [ 25.794790] PGD 1c84a9067 [ 25.797442] PUD 1c84af067 PMD 0 [ 25.800974] [ 25.802593] Oops: 0002 [#1] PREEMPT SMP KASAN [ 25.807061] Dumping ftrace buffer: [ 25.810576] (ftrace buffer empty) [ 25.814261] Modules linked in: [ 25.817543] CPU: 1 PID: 3786 Comm: syz-executor877 Not tainted 4.9.119-g9dc978d #23 [ 25.825307] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 25.834639] task: ffff8801bb42b000 task.stack: ffff8801b93a0000 [ 25.840669] RIP: 0010:[<ffffffff836bf9cc>] [<ffffffff836bf9cc>] l2tp_session_free+0x11c/0x200 [ 25.849566] RSP: 0018:ffff8801b93a7ca0 EFLAGS: 00010246 [ 25.855094] RAX: dffffc0000000000 RBX: ffff8801b943bb80 RCX: 0000000000000000 [ 25.862339] RDX: 1ffff10037262a10 RSI: ffffffff836bf9a1 RDI: ffff8801b9315080 [ 25.869580] RBP: ffff8801b93a7cc0 R08: ffff8801bb42b8e8 R09: 0000000000000000 [ 25.876829] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b9314f00 [ 25.884074] R13: ffff8801b943bb88 R14: 0000000000000000 R15: ffffffff83015be0 [ 25.891320] FS: 00000000017c3880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 25.899562] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 25.905422] CR2: 0000000000000080 CR3: 00000001cc584000 CR4: 00000000001606f0 [ 25.912668] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 25.919910] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 25.927155] Stack: [ 25.929282] ffff8801b8d33b80 ffff8801b943bb80 ffff8801b8d33f50 ffff8801b8d33e58 [ 25.937281] ffff8801b93a7ce8 ffffffff836c72b2 ffff8801b8d33fc0 ffff8801b8d33b80 [ 25.945272] ffffffff836c71e0 ffff8801b93a7d20 ffffffff830230f5 ffff8801b8d33fc0 [ 25.953284] Call Trace: [ 25.955855] [<ffffffff836c72b2>] pppol2tp_session_destruct+0xd2/0x110 [ 25.962495] [<ffffffff836c71e0>] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 25.968794] [<ffffffff830230f5>] __sk_destruct+0x55/0x590 [ 25.974398] [<ffffffff83015be0>] ? sock_release+0x1c0/0x1c0 [ 25.980170] [<ffffffff8302ab83>] sk_destruct+0x63/0x80 [ 25.985573] [<ffffffff8302abef>] __sk_free+0x4f/0x220 [ 25.990830] [<ffffffff8302adeb>] sk_free+0x2b/0x40 [ 25.995826] [<ffffffff836ca5b9>] pppol2tp_release+0x239/0x2e0 [ 26.001779] [<ffffffff83015ab6>] sock_release+0x96/0x1c0 [ 26.007292] [<ffffffff83015bf6>] sock_close+0x16/0x20 [ 26.012552] [<ffffffff81578693>] __fput+0x263/0x700 [ 26.017629] [<ffffffff81578bb5>] ____fput+0x15/0x20 [ 26.022715] [<ffffffff8119838c>] task_work_run+0x10c/0x180 [ 26.028404] [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 [ 26.034694] [<ffffffff810064d4>] do_syscall_64+0x364/0x490 [ 26.040380] [<ffffffff839fccd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 26.047276] 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 f5 f0 c9 fd 4c 89 ea 48 b8 00 [ 26.074371] RIP [<ffffffff836bf9cc>] l2tp_session_free+0x11c/0x200 [ 26.080884] RSP <ffff8801b93a7ca0> [ 26.084481] CR2: 0000000000000080 [ 26.088193] ---[ end trace 836498cd35d0b036 ]--- [ 26.092952] Kernel panic - not syncing: Fatal exception [ 26.098671] Dumping ftrace buffer: [ 26.102191] (ftrace buffer empty) [ 26.105918] Kernel Offset: disabled [ 26.109528] Rebooting in 86400 seconds..