linux-kernel - RE: [PATCH] mce: use safe MSR accesses

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: <3908561D78D1C84285E8C5FCA982C28F32A0E42D@ORSMSX113.amr.corp.intel.com>
Date:	Wed, 11 Mar 2015 22:47:04 +0000
From:	"Luck, Tony" <tony.luck@...el.com>
To:	"jesse.larrew@....com" <jesse.larrew@....com>,
	"x86@...nel.org" <x86@...nel.org>
CC:	Joel Schopp <joel.schopp@....com>, Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] mce: use safe MSR accesses

> When running as a guest under kvm, it's possible that the MSR
> being accessed may not be implemented. All MSR accesses should
> be prepared to handle exceptions.

Isn't that a KVM bug?  The code here first checks family/model before accessing the MSR:

                 if (c->x86 == 0x15 &&
                     (c->x86_model >= 0x10 && c->x86_model <= 0x1f)) {

If kvm tells the guest that it is running on one of these models, shouldn't it provide
complete coverage for that model?

If that isn't possible - then you should still do more than just s/rdmsrl/rdmsrl_safe/ ... like
check the return value to see whether you got an exception .. and thus should skip past
code that uses the "val" that you thought you read from the non-existent MSR.

-Tony

--
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/