linux-kernel - Re: [PATCH] x86: svm: don't intercept CR0 TS or MP bit write

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, 24 Feb 2015 15:25:03 -0600
From:	Joel Schopp <joel.schopp@....com>
To:	Radim Krčmář <rkrcmar@...hat.com>
CC:	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>, <kvm@...r.kernel.org>,
	Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...en8.de>,
	<linux-kernel@...r.kernel.org>, David Kaplan <david.kaplan@....com>
Subject: Re: [PATCH] x86: svm: don't intercept CR0 TS or MP bit write


>> -		clr_cr_intercept(svm, INTERCEPT_CR0_WRITE);
>>  	} else {
>>  		set_cr_intercept(svm, INTERCEPT_CR0_READ);
> (There is no point in checking fpu_active if cr0s are equal.)
>
>> -		set_cr_intercept(svm, INTERCEPT_CR0_WRITE);
> KVM uses lazy FPU and the state is undefined before the first access.
> We set cr0.ts when !svm->vcpu.fpu_active to detect the first access, but
> if we allow the guest to clear cr0.ts without exiting, it can access FPU
> with undefined state.
Thanks for the valuable feedback.  It's apparent I hadn't thought
through the interaction with lazy FPU and will need to go back and
rethink my approach here.
--
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/