linux-kernel - Re: [PATCH 00/31 v2] PTI support for x86

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Message-ID: <20180222111003.GB22572@kroah.com>
Date:   Thu, 22 Feb 2018 12:10:03 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Lorenzo Colitti <lorenzo@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mark D Rustad <mrustad@...il.com>,
        Adam Borowski <kilobyte@...band.pl>,
        Joerg Roedel <jroedel@...e.de>,
        Andy Lutomirski <luto@...nel.org>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Brian Gerst <brgerst@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Eduardo Valentin <eduval@...zon.com>,
        Will Deacon <will.deacon@....com>,
        "Liguori, Anthony" <aliguori@...zon.com>,
        Daniel Gruss <daniel.gruss@...k.tugraz.at>,
        Hugh Dickins <hughd@...gle.com>,
        Kees Cook <keescook@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Waiman Long <llong@...hat.com>, Pavel Machek <pavel@....cz>,
        Florian Westphal <fw@...len.de>
Subject: Re: [PATCH 00/31 v2] PTI support for x86_32

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@...gle.com> wrote:
> > On Wed, Feb 14, 2018 at 5:54 PM, Greg KH <gregkh@...uxfoundation.org> 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