Re: [PATCH] libnvdimm/pmem: Bypass CONFIG_HARDENED_USERCOPY overhead

Jan Kara
2019-05-20T07:52:33Z

On Sat 18-05-19 21:46:03, Dan Williams wrote:
> On Fri, May 17, 2019 at 12:25 PM Kees Cook <keescook@chromium.org> wrote:
> > On Fri, May 17, 2019 at 10:28:48AM -0700, Dan Williams wrote:
> > > It seems dax_iomap_actor() is not a path where we'd be worried about
> > > needing hardened user copy checks.
> >
> > I would agree: I think the proposed patch makes sense. :)
>
> Sounds like an acked-by to me.

Yeah, if Kees agrees, I'm fine with skipping the checks as well. I just
wanted that to be clarified. Also it helped me that you wrote:

That routine (dax_iomap_actor()) validates that the logical file offset is
within bounds of the file, then it does a sector-to-pfn translation which
validates that the physical mapping is within bounds of the block device.

That is more specific than "dax_iomap_actor() takes care of necessary
checks" which was in the changelog. And the above paragraph helped me
clarify which checks in dax_iomap_actor() you think replace those usercopy
checks. So I think it would be good to add that paragraph to those
copy_from_pmem() functions as a comment just in case we are wondering in
the future why we are skipping the checks... Also feel free to add:

Acked-by: Jan Kara <jack@suse.cz>

Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR