Re: [PATCH v11 21/48] ext4: Add richacl feature flag

[Austin S Hemmelgarn]

On 2015-10-16 13:41, Andreas Gruenbacher wrote:
> On Fri, Oct 16, 2015 at 7:31 PM, Austin S Hemmelgarn
> <ahferroin7@xxxxxxxxx> wrote:
> > I would like to re-iterate, on both XFS and ext4, I _really_ think this
> > should be a ro_compat flag, and not an incompat one.  If a person has the
> > ability to mount the FS (even if it's a read-only mount), then they by
> > definition have read access to the file or partition that the filesystem is
> > contained in, which means that any ACL's stored on the filesystem are
> > functionally irrelevant,
>
> It is unfortunately not safe to make such a file system accessible to
> other users, so the feature is not strictly read-only compatible.
OK, seeing as I wasn't particularly clear as to why I object to this in 
my other e-mail, let's try this again.

Can you please explain exactly why it isn't safe to make such a 
filesystem accessible to other users?  Because that _really_ sounds to 
me like you are trying to rely on this being un-mountable on a kernel 
that doesn't support richacls to try and provide the illusion of better 
security.

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