[....] Starting enhanced syslogd: rsyslogd[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.298256] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 18.552605] random: sshd: uninitialized urandom read (32 bytes read) [ 18.899234] random: sshd: uninitialized urandom read (32 bytes read) [ 19.390166] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.58' (ECDSA) to the list of known hosts. [ 28.368454] urandom_read: 1 callbacks suppressed [ 28.368457] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 28.569728] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 28.578083] IP: [] l2tp_session_free+0x11c/0x200 [ 28.584505] PGD 1ca6c9067 [ 28.587150] PUD 1c9e68067 PMD 0 [ 28.590728] [ 28.592375] Oops: 0002 [#1] PREEMPT SMP KASAN [ 28.596918] Dumping ftrace buffer: [ 28.600436] (ftrace buffer empty) [ 28.604123] Modules linked in: [ 28.607414] CPU: 0 PID: 3807 Comm: syz-executor796 Not tainted 4.9.124-g09eb2ba #31 [ 28.615178] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 28.624510] task: ffff8801b6d14800 task.stack: ffff8801b7d68000 [ 28.630548] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 28.639399] RSP: 0018:ffff8801b7d6fc98 EFLAGS: 00010246 [ 28.644818] RAX: dffffc0000000000 RBX: ffff8801b5af0000 RCX: 0000000000000000 [ 28.652063] RDX: 1ffff10036d58ba0 RSI: ffffffff836c4711 RDI: ffff8801b6ac5d00 [ 28.659309] RBP: ffff8801b7d6fcb8 R08: ffff8801b6d150e8 R09: 0000000000000000 [ 28.666549] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b6ac5b80 [ 28.673789] R13: ffff8801b5af0008 R14: 0000000000000000 R15: 0000000000000000 [ 28.681033] FS: 0000000001cb4880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 28.689244] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 28.695097] CR2: 0000000000000080 CR3: 00000001b7ed3000 CR4: 00000000001606f0 [ 28.702339] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 28.709581] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 28.716820] Stack: [ 28.718958] ffff8801cb270000 ffff8801b5af0000 ffff8801cb2703d0 ffff8801cb2702d8 [ 28.726980] ffff8801b7d6fce0 ffffffff836cc022 ffff8801cb270440 ffff8801cb270000 [ 28.735070] ffffffff836cbf50 ffff8801b7d6fd18 ffffffff830281f5 ffff8801cb270440 [ 28.743051] Call Trace: [ 28.745611] [] pppol2tp_session_destruct+0xd2/0x110 [ 28.752278] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 28.758570] [] __sk_destruct+0x55/0x590 [ 28.764164] [] sk_destruct+0x63/0x80 [ 28.769496] [] __sk_free+0x4f/0x220 [ 28.774833] [] sk_free+0x2b/0x40 [ 28.779835] [] pppol2tp_release+0x239/0x2e0 [ 28.785796] [] __sock_release+0xd7/0x260 [ 28.791477] [] ? __sock_release+0x260/0x260 [ 28.797418] [] sock_close+0x19/0x20 [ 28.802668] [] __fput+0x263/0x700 [ 28.807739] [] ____fput+0x15/0x20 [ 28.812816] [] task_work_run+0x10c/0x180 [ 28.818503] [] exit_to_usermode_loop+0xfc/0x120 [ 28.824792] [] do_syscall_64+0x364/0x490 [ 28.830479] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 28.837371] 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 [ 28.864394] RIP [] l2tp_session_free+0x11c/0x200 [ 28.870892] RSP [ 28.874486] CR2: 0000000000000080 [ 28.878140] ---[ end trace 3d54fa0beef0142a ]--- [ 28.882993] Kernel panic - not syncing: Fatal exception [ 28.888672] Dumping ftrace buffer: [ 28.892205] (ftrace buffer empty) [ 28.895895] Kernel Offset: disabled [ 28.899495] Rebooting in 86400 seconds..