Re: [PATCH 0/2] ima: policy search speedup

[Dave Chinner <david@fromorbit.com>]

On Tue, Dec 11, 2012 at 02:07:22PM -0500, Mimi Zohar wrote:
> On Tue, 2012-12-11 at 13:09 -0500, Eric Paris wrote:
> > On Tue, Dec 11, 2012 at 12:55 PM, Linus Torvalds
> > <torvalds@linux-foundation.org> wrote:
> > 
> > > And your "pseudo-filesystems" argument is pretty stupid too, since WE
> > > ALREADY HAVE A FLAG FOR THAT!
> > >
> > > Guess where it is? Oh, it's in the place I already mentioned makes
> > > more sense. Look for S_PRIVATE in inode->i_flags, and IS_PRIVATE() in
> > > users. It's what the other security models already use to avoid
> > > bothering calling down to the security layers. The fact that the
> > > integrity layer bypasses the normal security layer in
> > > ima_file_check(), for example, is no excuse to then make up totally
> > > new flags.
> > 
> > IS_PRIVATE() is not used by and darn well better not be used by, all
> > psuedo filesystems like procfs which IMA may want to ignore.  LSMs
> > like to do control on them.  I thought S_PRIVATE was really only used
> > by the anon_inode and reiserfs's really crazy ass internal inodes.  I
> > could always be wrong.
> 
> I was actually wondering about the MS_NOSEC flag.  It's currently being
> used by fuse, gfs2, ocfs2 and tmpfs.  (Not sure about xfs.)  Can someone
> explain what it is being used for?

For determining whether to clearing suid bits on writes to a
file. It defaults to on for all filesystems that use mount_bdev(),
which is just about every local filesystem (include XFS).

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com