x86/kvm: Update spectre-v1 mitigation (085331df) · Commits · 戴 / test

Commit "KVM: x86: Add memory barrier on vmcs field lookup" added a raw 'asm("lfence");' to prevent a bounds check bypass of 'vmcs_field_to_offset_table'. The lfence can be avoided in this path by using the array_index_nospec() helper designed for these types of fixes. Signed-off-by:

Dan Williams <dan.j.williams@intel.com> Signed-off-by:

Thomas Gleixner <tglx@linutronix.de> Acked-by:

Paolo Bonzini <pbonzini@redhat.com> Cc: Andrew Honig <ahonig@google.com> Cc: kvm@vger.kernel.org Cc: Jim Mattson <jmattson@google.com> Link: https://lkml.kernel.org/r/151744959670.6342.3001723920950249067.stgit@dwillia2-desk3.amr.corp.intel.com

arch/x86/kvm/vmx.c

+9 −11

Original line number	Diff line number	Diff line
		@@ -34,6 +34,7 @@
		#include <linux/tboot.h>
		#include <linux/hrtimer.h>
		#include <linux/frame.h>
		#include <linux/nospec.h>
		#include "kvm_cache_regs.h"
		#include "x86.h"

		@@ -898,21 +899,18 @@ static const unsigned short vmcs_field_to_offset_table[] = {

		static inline short vmcs_field_to_offset(unsigned long field)
		{
		BUILD_BUG_ON(ARRAY_SIZE(vmcs_field_to_offset_table) > SHRT_MAX);
		const size_t size = ARRAY_SIZE(vmcs_field_to_offset_table);
		unsigned short offset;

		if (field >= ARRAY_SIZE(vmcs_field_to_offset_table))
		BUILD_BUG_ON(size > SHRT_MAX);
		if (field >= size)
		return -ENOENT;

		/*
		* FIXME: Mitigation for CVE-2017-5753. To be replaced with a
		* generic mechanism.
		*/
		asm("lfence");

		if (vmcs_field_to_offset_table[field] == 0)
		field = array_index_nospec(field, size);
		offset = vmcs_field_to_offset_table[field];
		if (offset == 0)
		return -ENOENT;

		return vmcs_field_to_offset_table[field];
		return offset;
		}

		static inline struct vmcs12 get_vmcs12(struct kvm_vcpu vcpu)

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