[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 15.727485] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 27.512856] random: sshd: uninitialized urandom read (32 bytes read) [ 28.050506] random: sshd: uninitialized urandom read (32 bytes read) [ 28.455607] random: sshd: uninitialized urandom read (32 bytes read) [ 28.585816] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.63' (ECDSA) to the list of known hosts. [ 34.155144] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 34.359740] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 34.368080] IP: [] l2tp_session_free+0x11c/0x200 [ 34.374507] PGD 1bcd68067 [ 34.377149] PUD 1b9e33067 PMD 0 [ 34.380625] [ 34.382243] Oops: 0002 [#1] PREEMPT SMP KASAN [ 34.386756] Dumping ftrace buffer: [ 34.390275] (ftrace buffer empty) [ 34.393972] Modules linked in: [ 34.397266] CPU: 0 PID: 3791 Comm: syz-executor721 Not tainted 4.9.124-g09eb2ba #31 [ 34.405033] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 34.414364] task: ffff8801b9ebb000 task.stack: ffff8801d9b50000 [ 34.420394] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 34.429495] RSP: 0018:ffff8801d9b57c98 EFLAGS: 00010246 [ 34.434922] RAX: dffffc0000000000 RBX: ffff8801c7fc9900 RCX: 0000000000000000 [ 34.442168] RDX: 1ffff10038d06cd0 RSI: ffffffff836c4711 RDI: ffff8801c6836680 [ 34.449412] RBP: ffff8801d9b57cb8 R08: ffff8801b9ebb8e8 R09: 0000000000000000 [ 34.456671] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c6836500 [ 34.464017] R13: ffff8801c7fc9908 R14: 0000000000000000 R15: 0000000000000000 [ 34.471265] FS: 00000000010f0880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 34.479468] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 34.485340] CR2: 0000000000000080 CR3: 00000001bcd79000 CR4: 00000000001606f0 [ 34.492587] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 34.500046] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 34.507290] Stack: [ 34.509414] ffff8801c1427700 ffff8801c7fc9900 ffff8801c1427ad0 ffff8801c14279d8 [ 34.517585] ffff8801d9b57ce0 ffffffff836cc022 ffff8801c1427b40 ffff8801c1427700 [ 34.525596] ffffffff836cbf50 ffff8801d9b57d18 ffffffff830281f5 ffff8801c1427b40 [ 34.533727] Call Trace: [ 34.536294] [] pppol2tp_session_destruct+0xd2/0x110 [ 34.542938] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 34.549340] [] __sk_destruct+0x55/0x590 [ 34.554994] [] sk_destruct+0x63/0x80 [ 34.560379] [] __sk_free+0x4f/0x220 [ 34.565635] [] sk_free+0x2b/0x40 [ 34.570737] [] pppol2tp_release+0x239/0x2e0 [ 34.576684] [] __sock_release+0xd7/0x260 [ 34.582367] [] ? __sock_release+0x260/0x260 [ 34.588309] [] sock_close+0x19/0x20 [ 34.593560] [] __fput+0x263/0x700 [ 34.598648] [] ____fput+0x15/0x20 [ 34.603735] [] task_work_run+0x10c/0x180 [ 34.609547] [] exit_to_usermode_loop+0xfc/0x120 [ 34.615953] [] do_syscall_64+0x364/0x490 [ 34.621655] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 34.628550] 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 a5 c5 c9 fd 4c 89 ea 48 b8 00 [ 34.655442] RIP [] l2tp_session_free+0x11c/0x200 [ 34.661944] RSP [ 34.665547] CR2: 0000000000000080 [ 34.669648] ---[ end trace 4e1066441be06263 ]--- [ 34.674427] Kernel panic - not syncing: Fatal exception [ 34.680069] Dumping ftrace buffer: [ 34.683589] (ftrace buffer empty) [ 34.687274] Kernel Offset: disabled [ 34.690875] Rebooting in 86400 seconds..