Re: IMA policy search speedup

[Al Viro]

On Wed, Sep 19, 2012 at 02:21:56PM +1000, James Morris wrote:
> On Tue, 18 Sep 2012, Kasatkin, Dmitry wrote:
> 
> > I looked to <linux/fs.h> and found that there is a possibility to to
> > add additional flag for sb->s_flags.
> > For example
> > 
> > #define MS_NOT_IMA              (1<<25) /* NOT_IMA */
> > #define IS_I_NOT_IMA(inode)   __IS_FLG(inode, MS_NOT_IMA)
> > 
> > 
> > Another way is to add additional dedicated integrity related member to
> > the sb structure.
> > struct super_block {
> > ...
> > #ifdef CONFIG_INTEGRITY
> >       int s_integrity;
> > #endif
> > };
> > 
> > Obviously there are only few super blocks in the system and few bytes
> > will not harm.
> 
> The flag seems better than adding a new struct member.  Why would you need 
> an int for this?

Per-superblock bit would be a bit better, but I really hate the way we have
them mixed up between superblock ->s_flags bits and mount(2) action weirdly
encoded into flags thing.  If we are going to touch that thing, how about
separate S_... bits, with MS_... crap left only for mount(2) decoding?  Mapped
to S_... when needed.

The really messy part is that right now we silently ignore all the unknown
bits in mount(2) flags argument ;-/  It's *not* a widely used syscall, but
still - changing that in a non-trivial way is potential userland breakage.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/