[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.656079] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 22.206958] random: sshd: uninitialized urandom read (32 bytes read) [ 22.558713] random: sshd: uninitialized urandom read (32 bytes read) [ 23.070986] random: sshd: uninitialized urandom read (32 bytes read) [ 29.612185] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.49' (ECDSA) to the list of known hosts. [ 35.092559] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 35.313812] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 35.322109] IP: [] l2tp_session_free+0x11c/0x200 [ 35.328551] PGD 1ca62e067 [ 35.331205] PUD 1c4c99067 PMD 0 [ 35.334713] [ 35.336468] Oops: 0002 [#1] PREEMPT SMP KASAN [ 35.340947] Dumping ftrace buffer: [ 35.344468] (ftrace buffer empty) [ 35.348167] Modules linked in: [ 35.351632] CPU: 1 PID: 3808 Comm: syz-executor020 Not tainted 4.9.120-gf85543b #76 [ 35.359416] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 35.368768] task: ffff8801b99c1800 task.stack: ffff8801d9188000 [ 35.374872] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 35.383774] RSP: 0018:ffff8801d918fca0 EFLAGS: 00010246 [ 35.389208] RAX: dffffc0000000000 RBX: ffff8801b7fb3680 RCX: 0000000000000000 [ 35.396461] RDX: 1ffff100394bbfa0 RSI: ffffffff836c29a1 RDI: ffff8801ca5dfd00 [ 35.403722] RBP: ffff8801d918fcc0 R08: ffff8801b99c20e8 R09: 0000000000000000 [ 35.410989] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801ca5dfb80 [ 35.418246] R13: ffff8801b7fb3688 R14: 0000000000000000 R15: ffffffff83018be0 [ 35.425502] FS: 0000000000a0f880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 35.433727] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 35.439594] CR2: 0000000000000080 CR3: 00000001c93c7000 CR4: 00000000001606f0 [ 35.446856] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 35.454126] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 35.461379] Stack: [ 35.463512] ffff8801b72e3b80 ffff8801b7fb3680 ffff8801b72e3f50 ffff8801b72e3e58 [ 35.471554] ffff8801d918fce8 ffffffff836ca2b2 ffff8801b72e3fc0 ffff8801b72e3b80 [ 35.479600] ffffffff836ca1e0 ffff8801d918fd20 ffffffff830260f5 ffff8801b72e3fc0 [ 35.487650] Call Trace: [ 35.490223] [] pppol2tp_session_destruct+0xd2/0x110 [ 35.496875] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 35.503310] [] __sk_destruct+0x55/0x590 [ 35.508934] [] ? sock_release+0x1c0/0x1c0 [ 35.514717] [] sk_destruct+0x63/0x80 [ 35.520185] [] __sk_free+0x4f/0x220 [ 35.525450] [] sk_free+0x2b/0x40 [ 35.530529] [] pppol2tp_release+0x239/0x2e0 [ 35.536492] [] sock_release+0x96/0x1c0 [ 35.542015] [] sock_close+0x16/0x20 [ 35.547389] [] __fput+0x263/0x700 [ 35.552484] [] ____fput+0x15/0x20 [ 35.557590] [] task_work_run+0x10c/0x180 [ 35.563436] [] exit_to_usermode_loop+0xfc/0x120 [ 35.569932] [] do_syscall_64+0x364/0x490 [ 35.575644] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 35.582639] 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 15 de c9 fd 4c 89 ea 48 b8 00 [ 35.609838] RIP [] l2tp_session_free+0x11c/0x200 [ 35.616348] RSP [ 35.619949] CR2: 0000000000000080 [ 35.623517] ---[ end trace e46c777f08cc12d4 ]--- [ 35.628276] Kernel panic - not syncing: Fatal exception [ 35.633920] Dumping ftrace buffer: [ 35.637440] (ftrace buffer empty) [ 35.641122] Kernel Offset: disabled [ 35.644723] Rebooting in 86400 seconds..