On Tue, Jan 09, 2018 at 12:24:12PM -0500, Stephen Smalley wrote:
> On Tue, 2018-01-09 at 16:56 +0000, Richard Haines wrote:
> > On Tue, 2018-01-09 at 10:11 -0500, Stephen Smalley wrote:
> > > On Mon, 2018-01-08 at 16:10 +0100, Vit Mojzis wrote:
> > > > Hi all,
> > > > there seems to be a discrepancy between man page and actual
> > > > behavior
> > > > of 
> > > > selabel_lookup() with MEDIA backend.
> > > > selabel_media man page says:
> > > >      "Should there not be a valid entry in the media file, then
> > > > the 
> > > > default removable_context file will be read (see
> > > > removable_context(5))."
> > > > 
> > > > but the removable_context file is never used (for more details
> > > > and
> > > > a 
> > > > reproducer see https://bugzilla.redhat.com/show_bug.cgi?id=139562
> > > > 1)
> > > > .
> > > > 
> > > > I can see two possible solutions:
> > > >    1) Remove the removable_context file and adjust man pages
> > > > accordingly.
> > > > 
> > > >    2) (Probably better) Add mechanism for using the
> > > > removable_context
> > > > 
> > > > Which one would you prefer?
> > > > 
> > > > In case of the latter, would adding the content of
> > > > removable_context 
> > > > file to saved_data->spec_arr[nspec + 1] (label_media.c) and
> > > > returning
> > > > it 
> > > > in case lookup fails be a reasonable solution?
> > > > 
> > > > Thank you.
> > > 
> > > It appears that selinux_removable_context_path() and the
> > > removable_context configuration were added by Dan Walsh in 2004 for
> > > use
> > > by an external caller.  The selabel_media backend wasn't introduced
> > > until 2007, and has never called selinux_removable_context_path()
> > > AFAICT.  The man page reference to removable_context in
> > > selabel_media.5
> > > was added by Richard Haines in 2011.  I think the man page is just
> > > wrong.  I don't know if there are any users of
> > > selinux_removable_context_path() still but we can't remove it
> > > without
> > > breaking ABI.
> > > 
> > 
> > As I screwed up the man page I'll fix, however would you prefer
> > option
> > 2 where it will check the removable_context file as I'm happy to do
> > that instead.
> 
> I don't think we should change the behavior of the label media backend,
> since this is not a regression in the code and altering it could have
> side effects on existing callers. I would appreciate it if someone
> could check whether selinux_removable_context_path() is in fact used by
> anything still, and if so, how (e.g. are they using it as a fallback in
> the event of selabel_lookup failure?). I couldn't seem to find any
> callers in the debian codesearch tool, but not sure if Fedora has
> anything equivalent?
> 

There's no such equivalent for Fedora. But I checked sources in Red Hat 
Enterprise
Linux and I didn't find anything what would use
selinux_removable_context_path().

Petr

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