[Samba] Strange logs: check_usershare_stat: file /var/lib/samba/usershares/ owned by uid 0 is not a regular file

[Jeremy Allison]

On Tue, Dec 01, 2020 at 08:10:52PM -0000, Roy Eastwood via samba wrote:
>Thanks Andrew for your quick reply.
>
>Here are the results of those commands:
>
>root at lxd-m1:~# ls -l /var/lib/samba/usershares
>total 0
>root at lxd-m1:~# ls -l /var/lib/samba/
>total 136
>-rw------- 1 root root          421888 Jun 16 19:18 account_policy.tdb
>drwxr-xr-x 1 root root              36 Jul 19  2019 DriverStore
>-rw------- 1 root root          425984 Jul 19  2019 group_mapping.tdb
>drwxr-xr-x 1 root root              98 Jul 19  2019 printers
>drwxr-xr-x 1 root root             124 Jul 19  2019 private
>-rw------- 1 root root          528384 Jul 19  2019 registry.tdb
>-rw------- 1 root root          421888 Jul 21  2019 share_info.tdb
>drwxrwx--T 1 root sambashare         0 Jul 19  2019 usershares
>-rw------- 1 root root           32768 Dec  1 19:57 winbindd_cache.tdb
>-rw-r--r-- 1 root root          421888 Jul 20  2019 winbindd_idmap.tdb
>drwxr-x--- 1 root winbindd_priv      8 Nov  4 17:08 winbindd_privileged
>root at lxd-m1:~# stat  /var/lib/samba/usershares
>  File: /var/lib/samba/usershares
>  Size: 0               Blocks: 0          IO Block: 4096   directory
>Device: 41h/65d Inode: 24656       Links: 1
>Access: (1770/drwxrwx--T)  Uid: (    0/    root)   Gid: (  111/sambashare)
>Access: 2020-12-01 19:00:10.120922818 +0000
>Modify: 2019-07-19 12:14:08.718571118 +0100
>Change: 2020-01-17 09:43:21.506782092 +0000
> Birth: -
>root at lxd-m1:~#

This is triggered by this code:

         if (!S_ISREG(psbuf->st_ex_mode)) {
                 DEBUG(0,("check_usershare_stat: file %s owned by uid %u is "
                         "not a regular file\n",
                         fname, (unsigned int)psbuf->st_ex_uid ));
                 return false;
         }

but it should be looking at the files inside /var/lib/samba/usershares,
not the /var/lib/samba/usershares directory itself.

This is called from load_usershare_service(), which is passed
the name of the share to find as a usershare. It looks like
this is being passed an empty "" string.