[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.331709] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 28.681778] random: sshd: uninitialized urandom read (32 bytes read) [ 28.902929] random: sshd: uninitialized urandom read (32 bytes read) [ 29.253825] random: sshd: uninitialized urandom read (32 bytes read) [ 44.178015] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.19' (ECDSA) to the list of known hosts. [ 49.702236] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 49.891286] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 49.899736] IP: [] l2tp_session_free+0x11c/0x200 [ 49.906153] PGD 1c876c067 [ 49.908792] PUD 1c8c08067 PMD 0 [ 49.912275] [ 49.913892] Oops: 0002 [#1] PREEMPT SMP KASAN [ 49.918372] Dumping ftrace buffer: [ 49.921882] (ftrace buffer empty) [ 49.925563] Modules linked in: [ 49.928845] CPU: 0 PID: 3782 Comm: syz-executor550 Not tainted 4.9.121-g681e57b #25 [ 49.936733] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 49.946055] task: ffff8801bcf54800 task.stack: ffff8801d9838000 [ 49.952140] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 49.960984] RSP: 0018:ffff8801d983fca0 EFLAGS: 00010246 [ 49.966413] RAX: dffffc0000000000 RBX: ffff8801c9e83b80 RCX: 0000000000000000 [ 49.973667] RDX: 1ffff100393eb300 RSI: ffffffff836c29a1 RDI: ffff8801c9f59800 [ 49.980912] RBP: ffff8801d983fcc0 R08: ffff8801bcf550e8 R09: 0000000000000000 [ 49.988158] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c9f59680 [ 49.995402] R13: ffff8801c9e83b88 R14: 0000000000000000 R15: ffffffff83018be0 [ 50.002748] FS: 00000000012b9880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 50.010964] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 50.016829] CR2: 0000000000000080 CR3: 00000001c8789000 CR4: 00000000001606f0 [ 50.024075] Stack: [ 50.026198] ffff8801d9513300 ffff8801c9e83b80 ffff8801d95136d0 ffff8801d95135d8 [ 50.034210] ffff8801d983fce8 ffffffff836ca2b2 ffff8801d9513740 ffff8801d9513300 [ 50.042188] ffffffff836ca1e0 ffff8801d983fd20 ffffffff830260f5 ffff8801d9513740 [ 50.050153] Call Trace: [ 50.052709] [] pppol2tp_session_destruct+0xd2/0x110 [ 50.059348] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 50.065643] [] __sk_destruct+0x55/0x590 [ 50.071244] [] ? sock_release+0x1c0/0x1c0 [ 50.077016] [] sk_destruct+0x63/0x80 [ 50.082354] [] __sk_free+0x4f/0x220 [ 50.087606] [] sk_free+0x2b/0x40 [ 50.092595] [] pppol2tp_release+0x239/0x2e0 [ 50.098538] [] sock_release+0x96/0x1c0 [ 50.104052] [] sock_close+0x16/0x20 [ 50.109304] [] __fput+0x263/0x700 [ 50.114519] [] ____fput+0x15/0x20 [ 50.119594] [] task_work_run+0x10c/0x180 [ 50.125287] [] exit_to_usermode_loop+0xfc/0x120 [ 50.131577] [] do_syscall_64+0x364/0x490 [ 50.137356] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 50.144249] 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 65 df c9 fd 4c 89 ea 48 b8 00 [ 50.171339] RIP [] l2tp_session_free+0x11c/0x200 [ 50.177838] RSP [ 50.181433] CR2: 0000000000000080 [ 50.185076] ---[ end trace 74f3e6ff47cf8f7c ]--- [ 50.189808] Kernel panic - not syncing: Fatal exception [ 50.195428] Dumping ftrace buffer: [ 50.198953] (ftrace buffer empty) [ 50.202643] Kernel Offset: disabled [ 50.206252] Rebooting in 86400 seconds..