linux-kernel - Re: [PATCH v2 0/2] Fix issue with alternatives/paravirt patches

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]

Date:	Tue, 26 Jul 2016 15:59:10 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Jessica Yu <jeyu@...hat.com>
Cc:	Miroslav Benes <mbenes@...e.cz>, Petr Mladek <pmladek@...e.com>,
	Jiri Kosina <jikos@...nel.org>,
	Chris J Arges <chris.j.arges@...onical.com>,
	Eugene Shatokhin <eugene.shatokhin@...alab.ru>,
	live-patching@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/2] Fix issue with alternatives/paravirt patches

On Thu, Jul 21, 2016 at 01:23:58AM -0400, Jessica Yu wrote:
> Hi,
> 
> A few months ago, Chris Arges reported a bug involving alternatives/paravirt
> patching that was discussed here [1] and here [2]. To briefly summarize the
> bug, patch modules that contained .altinstructions or .parainstructions
> sections would break because these alternative/paravirt patches would be
> applied first by the module loader (see x86 module_finalize()), then
> livepatch would later clobber these patches when applying per-object
> relocations. This lead to crashes and unpredictable behavior.
> 
> One conclusion we reached from our last discussion was that we will
> need to introduce some arch-specific code to address this problem.
> This patchset presents a possible fix for the bug by adding a new
> arch-specific arch_klp_init_object_loaded() function that by default
> does nothing but can be overridden by different arches.
> 
> To fix this issue for x86, since we can access a patch module's Elf
> sections through mod->klp_info, we can simply delay the calls to
> apply_paravirt() and apply_alternatives() to arch_klp_init_object_loaded(),
> which is called after relocations have been written for an object.
> In addition, for patch modules, .parainstructions and .altinstructions are
> prefixed by ".klp.arch.${objname}" so that the module loader ignores them
> and livepatch can apply them manually.
> 
> Currently for kpatch, we don't support including jump table sections in
> the patch module, and supporting .smp_locks is currently broken, so we
> don't consider those sections (for now).
> 
> I did some light testing with some patches to kvm and verified that the
> original issue reported in [2] was fixed.
> 
> Based on linux-next.

For the series:

Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>

-- 
Josh