Re: O_DIRECTORY

[Chuck Silvers <chuq%chuq.com@localhost>]

On Mon, Sep 13, 2010 at 12:59:40PM -0400, Steven Bellovin wrote:
> 
> On Sep 13, 2010, at 12:58 39PM, David Laight wrote:
> 
> > On Sat, Sep 11, 2010 at 02:01:43PM -0700, Chuck Silvers wrote:
> >> hi folks,
> >> 
> >> the remaining missing bit that prevents acroread from working with the new
> >> linux emulation code (PR 43695) is support for the O_DIRECTORY flag to 
> >> open().
> > 
> > Is there a way to open a directory on which you have neither read nor
> > write access (maybe not even search access) ?
> 
> You can only open something for which you have *some* access right.
> Traditionally, Unix has done access rights checking only at open time,
> not at read/write/chdir time.
> 
> > Sometimes it is necessary to open "." in order to do a later fchdir().
> > And if/when we support openat() then you have a good justification for
> > only requiring 'x' access.
> > 
> This poses an interesting question -- what flags should go in the open()
> call to permit search path but not read?


the POSIX-2008 web page that mentioned in my original mail describes
additional open() flags that address these issues.

-Chuck