linux-kernel - Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20160718095657.GA5374@gmail.com>
Date:	Mon, 18 Jul 2016 11:56:57 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Dave Hansen <dave.hansen@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Al Viro <viro@...iv.linux.org.uk>, X86 ML <x86@...nel.org>,
	Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux API <linux-api@...r.kernel.org>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-arch <linux-arch@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Arnd Bergmann <arnd@...db.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls


* Andy Lutomirski <luto@...capital.net> wrote:

> On Thu, Jul 14, 2016 at 1:07 AM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * Andy Lutomirski <luto@...capital.net> wrote:
> >
> >> On Wed, Jul 13, 2016 at 12:56 AM, Ingo Molnar <mingo@...nel.org> wrote:
> >> >
> >> > * Andy Lutomirski <luto@...capital.net> wrote:
> >> >
> >> >> > If we push a PKRU value into a thread between the rdpkru() and wrpkru(), we'll
> >> >> > lose the content of that "push".  I'm not sure there's any way to guarantee
> >> >> > this with a user-controlled register.
> >> >>
> >> >> We could try to insist that user code uses some vsyscall helper that tracks
> >> >> which bits are as-yet-unassigned.  That's quite messy, though.
> >> >
> >> > Actually, if we turned the vDSO into something more like a minimal user-space
> >> > library with the ability to run at process startup as well to prepare stuff
> >> > then it's painful to get right only *once*, and there will be tons of other
> >> > areas where a proper per thread data storage on the user-space side would be
> >> > immensely useful!
> >>
> >> Doing this could be tricky: how exactly is the vDSO supposed to find per-thread
> >> data without breaking existing glibc?
> >
> > So I think the way this could be done is by allocating it itself. The vDSO vma
> > itself is 'external' to glibc as well to begin with - this would be a small
> > extension to that concept.
> 
> But how does the vdso code find it?  FS and GS are both spoken for by existing 
> userspace.

Minimally relinking itself on a per mm basis?

Thanks,

	Ingo