[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c.
[....] Starting OpenBSD Secure Shell server: sshd[   32.113372] random: sshd: uninitialized urandom read (32 bytes read)
[?25l[?1c7[ ok 8[?25h[?0c.

Debian GNU/Linux 7 syzkaller ttyS0

syzkaller login: [   36.305711] random: sshd: uninitialized urandom read (32 bytes read)
[   36.637218] random: sshd: uninitialized urandom read (32 bytes read)
[   38.061794] random: sshd: uninitialized urandom read (32 bytes read)
[   38.301910] random: sshd: uninitialized urandom read (32 bytes read)
Warning: Permanently added '10.128.15.201' (ECDSA) to the list of known hosts.
[   43.808114] random: sshd: uninitialized urandom read (32 bytes read)
executing program
executing program
executing program
[   44.054264] ------------[ cut here ]------------
[   44.059068] kernel BUG at fs/userfaultfd.c:883!
[   44.063895] invalid opcode: 0000 [#1] SMP PTI
[   44.068408] CPU: 1 PID: 4550 Comm: syz-executor521 Not tainted 4.18.0-rc5+ #29
[   44.075764] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[   44.085146] RIP: 0010:userfaultfd_release+0x8a7/0xc30
[   44.090320] Code: ff 89 c0 48 89 c1 48 c1 e1 20 48 09 c1 49 89 0c 24 e9 9d fe ff ff 8b 7d a8 e8 65 24 d2 ff e9 af fe ff ff e8 db 6f 76 ff eb 27 <0f> 0b 0f 1f 80 00 00 00 00 eb fe 49 89 f5 44 89 ff e8 43 24 d2 ff 
[   44.109688] RSP: 0018:ffff8801bbb7fab8 EFLAGS: 00010202
[   44.115060] RAX: 0000000000000000 RBX: ffff8801ac62b300 RCX: 0000000000000000
[   44.122321] RDX: 00000000ffffff00 RSI: 0000000000000000 RDI: ffffea0009769b60
[   44.129583] RBP: ffff8801bbb7fbe0 R08: 0000000000000000 R09: 0000000000000002
[   44.136844] R10: 0000000000000000 R11: ffffffff81f1ac80 R12: 0000000000100273
[   44.144106] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[   44.151384] FS:  0000000001430880(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000
[   44.159604] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   44.165486] CR2: 00007f1f7cc5ce78 CR3: 00000001a815e000 CR4: 00000000001406e0
[   44.172748] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   44.180013] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   44.187287] Call Trace:
[   44.189907]  __fput+0x458/0xa30
[   44.193201]  ? fput+0x300/0x300
[   44.196488]  ____fput+0x37/0x40
[   44.199782]  task_work_run+0x22e/0x2b0
[   44.203671]  prepare_exit_to_usermode+0x35d/0x430
[   44.208525]  syscall_return_slowpath+0x108/0x800
[   44.213277]  ? __close_fd+0x47b/0x4d0
[   44.217091]  do_syscall_64+0x1ad/0x230
[   44.220989]  entry_SYSCALL_64_after_hwframe+0x63/0xe7
[   44.226172] RIP: 0033:0x405471
[   44.229352] Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 54 17 00 00 c3 48 83 ec 08 e8 6a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 b3 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01 
[   44.248698] RSP: 002b:00007ffd968decc0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
[   44.256406] RAX: 0000000000000000 RBX: 0000000000000005 RCX: 0000000000405471
[   44.263665] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
[   44.270937] RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
[   44.278208] R10: 00007ffd968decd0 R11: 0000000000000293 R12: 00000000006dbc3c
[   44.285470] R13: 00000000006dbda0 R14: 0000000000000008 R15: 0000000000000001
[   44.292737] Modules linked in:
[   44.295934] Dumping ftrace buffer:
[   44.299461]    (ftrace buffer empty)
[   44.303309] ---[ end trace 6d110da0ecb68d29 ]---
[   44.308167] RIP: 0010:userfaultfd_release+0x8a7/0xc30
[   44.313412] Code: ff 89 c0 48 89 c1 48 c1 e1 20 48 09 c1 49 89 0c 24 e9 9d fe ff ff 8b 7d a8 e8 65 24 d2 ff e9 af fe ff ff e8 db 6f 76 ff eb 27 <0f> 0b 0f 1f 80 00 00 00 00 eb fe 49 89 f5 44 89 ff e8 43 24 d2 ff 
[   44.333060] RSP: 0018:ffff8801bbb7fab8 EFLAGS: 00010202
[   44.338477] RAX: 0000000000000000 RBX: ffff8801ac62b300 RCX: 0000000000000000
[   44.345801] RDX: 00000000ffffff00 RSI: 0000000000000000 RDI: ffffea0009769b60
[   44.353117] RBP: ffff8801bbb7fbe0 R08: 0000000000000000 R09: 0000000000000002
[   44.360439] R10: 0000000000000000 R11: ffffffff81f1ac80 R12: 0000000000100273
[   44.367757] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[   44.375101] FS:  0000000001430880(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000
[   44.383378] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   44.389320] CR2: 00007f1f7cc5ce78 CR3: 00000001a815e000 CR4: 00000000001406e0
[   44.396642] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   44.403959] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   44.411323] Kernel panic - not syncing: Fatal exception
[   44.417186] Dumping ftrace buffer:
[   44.420719]    (ftrace buffer empty)
[   44.424415] Kernel Offset: disabled
[   44.428041] Rebooting in 86400 seconds..