linux-kernel - Re: [PATCH 1/1] Fix permission checking by NFS client for open-create with mode 000

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Date:	Fri, 11 Jul 2014 16:46:19 -0400
From:	Trond Myklebust <trond.myklebust@...marydata.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	Frank Filz <ffilzlnx@...dspring.com>,
	Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
	Linux Kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] Fix permission checking by NFS client for open-create
 with mode 000

On Fri, Jul 11, 2014 at 4:20 PM, J. Bruce Fields <bfields@...ldses.org> wrote:
>
> On Wed, Jul 09, 2014 at 07:12:09PM -0400, Trond Myklebust wrote:
> > Oops. Sorry, the correct sub-sub-sub-sub-....paragraph is this one:
> >
> >          Permission to execute a file.
> >
> >          Servers SHOULD allow a user the ability to read the data of the
> >          file when only the ACE4_EXECUTE access mask bit is allowed.
> >          This is because there is no way to execute a file without
> >          reading the contents.  Though a server may treat ACE4_EXECUTE
> >          and ACE4_READ_DATA bits identically when deciding to permit a
> >          READ operation, it SHOULD still allow the two bits to be set
> >          independently in ACLs, and MUST distinguish between them when
> >          replying to ACCESS operations.  In particular, servers SHOULD
> >          NOT silently turn on one of the two bits when the other is set,
> >          as that would make it impossible for the client to correctly
> >          enforce the distinction between read and execute permissions.
> >
> >
> > > To me that translates as saying that the server SHOULD accept an
> > > OPEN(SHARE_ACCESS_READ|SHARE_ACCESS_WRITE) request in the above
> > > situation.
> >
> > Same conclusion, though....
>
> Are we sure that's not just a spec bug?
>
> Allowing OPEN(BOTH) on a -wx file seems like a pretty weird result.

Sure, but you can do OPEN(SHARE_ACCESS_READ) and
OPEN(SHARE_ACCESS_WRITE) separately and end up with a stateid that
allows both reading and writing. What does preventing
OPEN(SHARE_ACCESS_BOTH) gain you in this context.?
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