linux-kernel - Re: [PATCH UPDATE] x86: ignore spurious faults

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: <200801251011.36934.ak@novell.com>
Date:	Fri, 25 Jan 2008 10:11:36 +0100
From:	Andi Kleen <ak@...ell.com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	"Jan Beulich" <jbeulich@...ell.com>,
	"Keir Fraser" <Keir.Fraser@...cam.ac.uk>,
	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Harvey Harrison" <harvey.harrison@...il.com>,
	"Matt Mackall" <mpm@...enic.com>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH UPDATE] x86: ignore spurious faults

On Friday 25 January 2008 09:38:38 Nick Piggin wrote:
> On Friday 25 January 2008 19:15, Jan Beulich wrote:
> > Actually, another thought: permitting (and handling) spurious faults for
> > kernel mappings conflicts with NMI handling, i.e. great care would be
> > needed to ensure the NMI path cannot touch any such mapping. So
> > even the present Xen/Linux Dom0 implementation may have some
> > (perhaps unlikely) problems here, and it would get worse if we added
> > e.g. a virtual watchdog NMI (something I am considering, which would
> > then extend the problem to DomU-s).
> 
> Can you explain how they conflict?

NMI is blocked by the hardware until IRET and when a page fault happens inside 
the NMI handler the early IRET unblocks it and then NMIs can nest, which
will lead to stack corruption.

-Andi

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/