Samba, GPFS, wordpad and create mask = 0777

[Richard Sharpe]

On Thu, Sep 1, 2011 at 11:55 AM, Richard Sharpe
<realrichardsharpe at gmail.com> wrote:
> On Wed, Aug 31, 2011 at 9:17 AM, Rolf Anders
> <rolf.anders at rz.uni-augsburg.de> wrote:
>> Jeremy,
>>
>> On Tue, Aug 30, 2011 at 10:16:09AM -0700, Jeremy Allison wrote:
>>> On Tue, Aug 30, 2011 at 10:14:19AM -0700, Richard Sharpe wrote:
>>> > Hi,
>>> >
>>> > Somewhere between Samba 3.5.3 and 3.5.8 a small change was made in
>>> > source3/smbd/open.c:open_file_ntcreate.
>>> >
>>> > The change was to change these lines:
>>> >
>>> >         if ((flags2 & O_CREAT) && lp_inherit_acls(SNUM(conn)) &&
>>> >             (def_acl = directory_has_default_acl(conn, parent_dir))) {
>>> >                 unx_mode = 0777;
>>> >         }
>>> >
>>> > to these:
>>> >
>>> >         if ((flags2 & O_CREAT) && lp_inherit_acls(SNUM(conn)) &&
>>> >             (def_acl = directory_has_default_acl(conn, parent_dir))) {
>>> >                 unx_mode = (0777 & lp_create_mask(SNUM(conn)));
>>> >         }
>>> >
>>> >
>>> > That is, lp_create_mask is anded with 0777 now, rather than 0777 being used.
>>> >
>>> > This causes a problem with wordpad on gpfs when you go to overwrite an
>>> > existing rtf file (seemingly because wordpad uses FILE_OVERWRITE_IF,
>>> > and saving any updates to an rtf file fails with "Unexpected error".
>>> >
>>> > I have tested with Word, Notepad and wordpad, and only wordpad seems
>>> > to use this behavior, and it seems very specific to GPFS.
>>> >
>>> > I do not yet have a test for the underlying problem, but I might develop one.
>>> >
>>> > The workaround is to add "create mask = 0777" to any GPFS-based shares.
>>>
>>> The change was correct. In the 3.5.3 code the explicit "create mask" setting
>>> was being ignored in this case - it should never be ignored when creating a
>>> new file.
>>
>> it seems to me that the value of "create mask" should actually be ignored
>> in this case, since it is only ignored if an ACL is inherited from the
>> parent directory.
>>
>> The description of "inherit acls" in smb.conf(5) as well as the
>> problem reported by Richard Sharpe suggest that a "create mask" which
>> is different from 0777 somehow interferes with ACL inheritance. Hence,
>> to make ACL inheritance work correctly, one would need to set "create
>> mask = 0777". This setting, however, would make all files world writable
>> that are created in a directory without inheritance.
>>
>> OTOH, if "create mask" really should take precedence over ACL inheritance,
>> at least the man page smb.conf(5) needs to be updated ("inherit acls (S)
>> [...] Enabling this option sets the unix mode to 0777, thus guaranteeing
>> that default directory acls are propagated.").
>
> While pursuing the underlying cause of this problem I have discovered
> that my test was incorrect and the change I mentioned above is not the
> culprit.
>
> Back to the drawing boards. Digging deeper.

OK, forget I spoke. The problem was that I moved the parameter
"gpfs:sharemodes = no" from being a global parameter to being a
per-share parameter in the smb.conf file we generate.

This broke things in relation to Wordpad. Now that I have moved it
back everything seems fine.

-- 
Regards,
Richard Sharpe