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Date: Mon, 15 Nov 2010 17:01:36 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
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Subject: Re: Executable bit check
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On Nov  5 14:47, Illia Bobyr wrote:
> On 11/5/2010 11:56 AM, Eric Blake wrote:
> > [...]
> > On Linux:
> >
> > $ setfacl -m mask:rwx d/f
> > $ getfacl d/f
> > # file: d/f
> > # owner: eblake
> > # group: eblake
> > user::rw-
> > user:dummy:rwx
> > group::rw-
> > mask::rwx
> > other::r--
> >
> > $ chmod -x d/f
> > $ getfacl d/f
> > # file: d/f
> > # owner: eblake
> > # group: eblake
> > user::rw-
> > user:dummy:rwx			#effective:rw-
> > group::rwx			#effective:rw-
> > mask::rw-
> > other::r--
> >
> > Interestingly - that means that on Linux, chmod -x changed the mask
> > entry of the ACLs, such that the effective permissions for the alternate
> > user are no longer permitted; so even though user dummy has rwx ACLs,
> > the mask prevents the user from executing the file any more.
> >
> > Cygwin does not emulate Linux in this regards at the moment, but now
> > that you have pointed out a simple test case, it may be possible to
> > patch cygwin1.dll to make the chmod() syscall affect the ACL mask as on
> > Linux.

That's very tricky.  The chmod function only gets a new mode_t value which
only applies to owner/group/others and the mask value.  The mask value
is changed by a chmod as well and non-default users and groups in the ACL
are only affected indirectly by the mask value which results in effective
permissions, as you can see above.

And here's the problem:

> It seems that setfacl also does not change the "mask" part on Cygwin:

There's no equivalent for the Solaris/POSIX mask value in the Windows ACL.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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