Re: Commit 13c164b1a186 - regression for LSMs/SELinux?

On Tue, 2020-09-29 at 20:00 +0200, Christoph Hellwig wrote:
> On Tue, Sep 29, 2020 at 10:23:50AM -0700, Linus Torvalds wrote:
> > On Tue, Sep 29, 2020 at 5:16 AM Ondrej Mosnacek <
> > [email protected]> wrote:
> > > OK, so it seems that reverting comes out as the best choice here.
> > 
> > Yeah.
> > 
> > > BTW, I'm looking at rw_verify_area() and I see this "If (ppos)"
> > > check
> > > and the comment above it... And then I look at autofs_write(),
> > > which
> > > passes &file->f_pos, while ksys_write() passes file_ppos(file)
> > 
> > Ok, that doesn't matter for the security_file_permission() issue,
> > but
> > yes, autofs is doing the traditional thing, and it's pointless.
> > Using
> > file_ppos(file) isn't an option since it's an inline to
> > read_write.c,
> > but it could just pass in NULL these days and avoid that too.
> > 
> > So how about we just do the appended patch? Can whoever sees this
> > problem just verify, even though it looks trivially correct...
> 
> This looks sensible to me.  I'd throw in a
> 
> /* only for autofs, don't use in new code */
> 
> near the export, but users of these kind of functions tend to be
> blind copy and paste code anyway, so the comment probably isn't
> even read by the relevant parties..

I'll build a patched kernel and give it a whirl.

Ian