Re: [PATCH 00/31 v2] PTI support for x86_32

[Greg KH]

On Wed, Feb 21, 2018 at 05:59:34PM +0100, Arnd Bergmann wrote:
> On Wed, Feb 21, 2018 at 11:26 AM, Lorenzo Colitti <lorenzo@xxxxxxxxxx> wrote:
> > On Wed, Feb 14, 2018 at 5:54 PM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> >> > > IPSEC doesn't work with a 64bit kernel and 32bit userspace right now.
> >> > >
> >> > > Back in 2015 someone started to work on that, and properly marked that
> >> > > the kernel could not handle this with commit 74005991b78a ("xfrm: Do not
> >> > > parse 32bits compiled xfrm netlink msg on 64bits host")
> >> > >
> >> > > This is starting to be hit by some Android systems that are moving
> >> > > (yeah, slowly) to 4.4 :(
> >> >
> >> > Does anybody have test-programs/harnesses for this?
> >>
> >> Lorenzo (now on the To: line), is the one that I think is looking into
> >> this, and should have some sort of test for it.  Lorenzo?
> >
> > Sorry for the late reply here. The issue is that the xfrm uapi structs
> > don't specify padding at the end, so they're a different size on
> > 32-bit and 64-bit archs. This by itself would be fine, as the kernel
> > could just ignore the (lack of) padding. But some of these structs
> > contain others (e.g., xfrm_userspi_info contains xfrm_usersa_info),
> > and in that case the whole layout after the contained struct is
> > different.
> 
> So this is x86 specific then and it already works correctly on all
> other architectures (especially arm64 Android), right?

Why is this an x86-specific issue?  I think people have noticed this
with ARM systems given that the original bug report I saw was for an
ARM Android-based system that had a 64bit kernel and 32bit userspace.

thanks,

greg k-h