[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 12.781683] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 30.166516] random: sshd: uninitialized urandom read (32 bytes read) [ 30.491639] random: sshd: uninitialized urandom read (32 bytes read) [ 30.813554] random: sshd: uninitialized urandom read (32 bytes read) [ 32.628283] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.5' (ECDSA) to the list of known hosts. [ 38.088308] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 38.294173] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 38.302456] IP: [] l2tp_session_free+0x11c/0x200 [ 38.308880] PGD 1ca15a067 [ 38.311519] PUD 1c9095067 PMD 0 [ 38.315005] [ 38.316626] Oops: 0002 [#1] PREEMPT SMP KASAN [ 38.321094] Dumping ftrace buffer: [ 38.324607] (ftrace buffer empty) [ 38.328293] Modules linked in: [ 38.331580] CPU: 1 PID: 3812 Comm: syz-executor336 Not tainted 4.9.117-g8b21e85 #71 [ 38.339345] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 38.349020] task: ffff8801b9353000 task.stack: ffff8801d90f8000 [ 38.355049] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 38.363912] RSP: 0018:ffff8801d90ffca0 EFLAGS: 00010246 [ 38.369334] RAX: dffffc0000000000 RBX: ffff8801c84f1900 RCX: 0000000000000000 [ 38.376586] RDX: 1ffff100390cf920 RSI: ffffffff836bf8f1 RDI: ffff8801c867c900 [ 38.384447] RBP: ffff8801d90ffcc0 R08: ffff8801b93538e8 R09: 0000000000000000 [ 38.391695] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c867c780 [ 38.398944] R13: ffff8801c84f1908 R14: 0000000000000000 R15: ffffffff83015be0 [ 38.406201] FS: 0000000001751880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 38.414489] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 38.420347] CR2: 0000000000000080 CR3: 00000001c913c000 CR4: 00000000001606f0 [ 38.427594] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 38.434851] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 38.442095] Stack: [ 38.444234] ffff8801d964bb80 ffff8801c84f1900 ffff8801d964bf50 ffff8801d964be58 [ 38.452520] ffff8801d90ffce8 ffffffff836c7202 ffff8801d964bfc0 ffff8801d964bb80 [ 38.460526] ffffffff836c7130 ffff8801d90ffd20 ffffffff83023095 ffff8801d964bfc0 [ 38.468543] Call Trace: [ 38.471119] [] pppol2tp_session_destruct+0xd2/0x110 [ 38.477764] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 38.484185] [] __sk_destruct+0x55/0x590 [ 38.489786] [] ? sock_release+0x1c0/0x1c0 [ 38.495558] [] sk_destruct+0x63/0x80 [ 38.500903] [] __sk_free+0x4f/0x220 [ 38.506166] [] sk_free+0x2b/0x40 [ 38.511165] [] pppol2tp_release+0x239/0x2e0 [ 38.517121] [] sock_release+0x96/0x1c0 [ 38.522632] [] sock_close+0x16/0x20 [ 38.527902] [] __fput+0x263/0x700 [ 38.533069] [] ____fput+0x15/0x20 [ 38.538158] [] task_work_run+0x10c/0x180 [ 38.543857] [] exit_to_usermode_loop+0xfc/0x120 [ 38.550151] [] do_syscall_64+0x364/0x490 [ 38.555848] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 38.562747] 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 e5 f1 c9 fd 4c 89 ea 48 b8 00 [ 38.589825] RIP [] l2tp_session_free+0x11c/0x200 [ 38.596501] RSP [ 38.600100] CR2: 0000000000000080 [ 38.603745] ---[ end trace 6dad1601e9b77eb2 ]--- [ 38.608506] Kernel panic - not syncing: Fatal exception [ 38.614185] Dumping ftrace buffer: [ 38.617709] (ftrace buffer empty) [ 38.621407] Kernel Offset: disabled [ 38.625009] Rebooting in 86400 seconds..