Commit 55cd57b5 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: x86: Filter out XTILE_CFG if XTILE_DATA isn't permitted 



Filter out XTILE_CFG from the supported XCR0 reported to userspace if the
current process doesn't have access to XTILE_DATA.  Attempting to set
XTILE_CFG in XCR0 will #GP if XTILE_DATA is also not set, and so keeping
XTILE_CFG as supported results in explosions if userspace feeds
KVM_GET_SUPPORTED_CPUID back into KVM and the guest doesn't sanity check
CPUID.

Fixes: 445ecdf7 ("kvm: x86: Exclude unpermitted xfeatures at KVM_GET_SUPPORTED_CPUID")
Reported-by: default avatarAaron Lewis <aaronlewis@google.com>
Reviewed-by: default avatarAaron Lewis <aaronlewis@google.com>
Tested-by: default avatarAaron Lewis <aaronlewis@google.com>
Link: https://lore.kernel.org/r/20230405004520.421768-3-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 6be3ae45

arch/x86/kvm/x86.h

+17 −1
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 
#define ARCH_X86_KVM_X86_H



#include <linux/kvm_host.h>

#include <asm/fpu/xstate.h>

#include <asm/mce.h>

#include <asm/pvclock.h>

#include "kvm_cache_regs.h"
@@ -325,7 +326,22 @@ extern bool enable_pmu; 
 */

static inline u64 kvm_get_filtered_xcr0(void)

{

	return kvm_caps.supported_xcr0 & xstate_get_guest_group_perm();

	u64 permitted_xcr0 = kvm_caps.supported_xcr0;



	BUILD_BUG_ON(XFEATURE_MASK_USER_DYNAMIC != XFEATURE_MASK_XTILE_DATA);



	if (permitted_xcr0 & XFEATURE_MASK_USER_DYNAMIC) {

		permitted_xcr0 &= xstate_get_guest_group_perm();



		/*

		 * Treat XTILE_CFG as unsupported if the current process isn't

		 * allowed to use XTILE_DATA, as attempting to set XTILE_CFG in

		 * XCR0 without setting XTILE_DATA is architecturally illegal.

		 */

		if (!(permitted_xcr0 & XFEATURE_MASK_XTILE_DATA))

			permitted_xcr0 &= ~XFEATURE_MASK_XTILE_CFG;

	}

	return permitted_xcr0;

}



static inline bool kvm_mpx_supported(void)