Re: [PATCH v3 3/3] mm/usercopy: Detect compound page overruns

Matthew Wilcox
2021-12-13T23:44:57Z

On Mon, Dec 13, 2021 at 12:52:22PM -0800, Kees Cook wrote:
> On Mon, Dec 13, 2021 at 02:27:03PM +0000, Matthew Wilcox (Oracle) wrote:
> > Move the compound page overrun detection out of
> > CONFIG_HARDENED_USERCOPY_PAGESPAN so it's enabled for more people.
>
> I'd argue that everything else enabled by USERCOPY_PAGESPAN could be
> removed now too. Do you want to add a 4th patch to rip that out?
>
> https://github.com/KSPP/linux/issues/163

I don't mind ... is it your assessment that it's not worth checking for
a copy_to/from_user that spans a boundary between a reserved and
!reserved page, or overlaps the boundary of rodata/bss/data/CMA?

I have no basis on which to judge that, so it's really up to you.