[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 15.484348] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 18.176872] random: sshd: uninitialized urandom read (32 bytes read) [ 18.497678] random: sshd: uninitialized urandom read (32 bytes read) [ 19.361273] random: sshd: uninitialized urandom read (32 bytes read) [ 19.490475] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.22' (ECDSA) to the list of known hosts. [ 24.946622] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 25.129230] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [ 25.137493] IP: [] l2tp_session_free+0x11c/0x200 [ 25.143945] PGD 1bd242067 [ 25.146588] PUD 1bf676067 PMD 0 [ 25.150083] [ 25.151713] Oops: 0002 [#1] PREEMPT SMP KASAN [ 25.156196] Dumping ftrace buffer: [ 25.159710] (ftrace buffer empty) [ 25.163396] Modules linked in: [ 25.166699] CPU: 1 PID: 3793 Comm: syz-executor406 Not tainted 4.9.113-g90e7a90 #16 [ 25.174466] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 25.183813] task: ffff8801b83ee000 task.stack: ffff8801c6c48000 [ 25.189857] RIP: 0010:[] [] l2tp_session_free+0x11c/0x200 [ 25.198714] RSP: 0018:ffff8801c6c4fca0 EFLAGS: 00010246 [ 25.204136] RAX: dffffc0000000000 RBX: ffff8801cb034000 RCX: 0000000000000000 [ 25.211382] RDX: 1ffff10039606a10 RSI: ffffffff836bdee1 RDI: ffff8801cb035080 [ 25.218627] RBP: ffff8801c6c4fcc0 R08: ffff8801b83ee8e8 R09: 0000000000000000 [ 25.225885] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801cb034f00 [ 25.233131] R13: ffff8801cb034008 R14: 0000000000000000 R15: ffffffff83014be0 [ 25.240379] FS: 0000000001c7e880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 [ 25.248607] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 25.254463] CR2: 0000000000000080 CR3: 00000001c507b000 CR4: 00000000001606f0 [ 25.261713] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 25.268958] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 25.276203] Stack: [ 25.278351] ffff8801c9479100 ffff8801cb034000 ffff8801c94794d0 ffff8801c94793d8 [ 25.286362] ffff8801c6c4fce8 ffffffff836c57f2 ffff8801c9479540 ffff8801c9479100 [ 25.294368] ffffffff836c5720 ffff8801c6c4fd20 ffffffff83022095 ffff8801c9479540 [ 25.302376] Call Trace: [ 25.304956] [] pppol2tp_session_destruct+0xd2/0x110 [ 25.311599] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 25.317894] [] __sk_destruct+0x55/0x590 [ 25.323493] [] ? sock_release+0x1c0/0x1c0 [ 25.329268] [] sk_destruct+0x63/0x80 [ 25.334606] [] __sk_free+0x4f/0x220 [ 25.339856] [] sk_free+0x2b/0x40 [ 25.344846] [] pppol2tp_release+0x239/0x2e0 [ 25.350800] [] sock_release+0x96/0x1c0 [ 25.356313] [] sock_close+0x16/0x20 [ 25.361568] [] __fput+0x263/0x700 [ 25.366649] [] ____fput+0x15/0x20 [ 25.371729] [] task_work_run+0x10c/0x180 [ 25.377423] [] exit_to_usermode_loop+0xfc/0x120 [ 25.383735] [] do_syscall_64+0x364/0x490 [ 25.389428] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 25.396325] 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 55 0b ca fd 4c 89 ea 48 b8 00 [ 25.423688] RIP [] l2tp_session_free+0x11c/0x200 [ 25.430209] RSP [ 25.433820] CR2: 0000000000000080 [ 25.437539] ---[ end trace e3d21adba2882fcf ]--- [ 25.442296] Kernel panic - not syncing: Fatal exception [ 25.448063] Dumping ftrace buffer: [ 25.451586] (ftrace buffer empty) [ 25.455268] Kernel Offset: disabled [ 25.458867] Rebooting in 86400 seconds..