[Samba] Leaking file descriptors in Version 4.13.17-Ubuntu

[Tinco Andringa]

Hi,

For about 2 weeks, I think since we updated smbd to version Version
4.13.17-Ubuntu we have encountered a "too many files open" error. I set out
to investigate and besides the limit being relatively low (~16500) I
noticed a very strange set of directory handles allocated by smbd:

```

root at big-data-1:/proc/11929# lsof |grep smbd |grep DIR| awk '{ print $9
}'|sort| uniq -c

     15 /

  16527 /big-data/wachtrij

      2 /big-data/wachtrij/processing

      4 /big-data/wachtrij/processing/P-CUSTOMER/Leeuwarden

     10 /big-data/wachtrij/processing/P-CUSTOMER/WF

     14 /big-data/wachtrij/processing/WF
```


There's over 16500 handles open to the root of one of the shares.
Restarting smbd dropped it to 0, and then over a period of 10 minutes it
has already increased to a thousand. There's only about 30 machines in this
network, of which only 10 are actively using this share for rendering
projects. Most of the clients are running windows, but there are 4 linux
clients as well. The rendering clients probably make very intensive use of
this samba share.

Is there a known (hopefully fixed) bug in 4.13.17, or is there something
wrong with our configuration? I am not much of an expert, and I did
recently blindly followed some performance optimization guides I found by
Googling around a bit, maybe I did something dumb:


[global]

workgroup = WORKGROUP

server string = %h server (Samba, Ubuntu)

log level = 1 auth_audit:3 auth_json_audit:3

log file = /var/log/samba/log.%m

max log size = 1000

logging = file

panic action = /usr/share/samba/panic-action %d

server role = standalone server

obey pam restrictions = yes

unix password sync = yes

passwd program = /usr/bin/passwd %u

passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:*
%n\n *password\supdated\ssuccessfully* .

pam password change = yes

map to guest = bad user

usershare allow guests = yes

allow insecure wide links = yes

[wachtrij]

path = /big-data/wachtrij

valid users = processing,preprocessing

comment =

browseable = yes

writeable = yes

read only = no

force create mode = 0660

force directory mode = 2770

force user = processing

force group = processing

follow symlinks = yes

wide links = yes

store dos attributes = no

ea support = no

map archive = no

map hidden = no

map system = no

map readonly = no

If there's no known bugs, and I haven't made any obvious configuration
mistakes, what's the best way to figure out what's going on, for example if
the handles are somehow legitimate? I suppose upgrading to the latest
upstream samba release would be the first step.

Kind regards,
Tinco