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Patch "kvm: vmx: Scrub hardware GPRs at VM-exit" has been added to the 4.14-stable tree

PATCH [email protected] 1 participant 1 message Jan 10, 2018

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This is a note to let you know that I've just added the patch titled

kvm: vmx: Scrub hardware GPRs at VM-exit

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-vmx-scrub-hardware-gprs-at-vm-exit.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 0cb5b30698fdc8f6b4646012e3acb4ddce430788 Mon Sep 17 00:00:00 2001

From: Jim Mattson <[email protected]>
Date: Wed, 3 Jan 2018 14:31:38 -0800
Subject: kvm: vmx: Scrub hardware GPRs at VM-exit

From: Jim Mattson <[email protected]>

commit 0cb5b30698fdc8f6b4646012e3acb4ddce430788 upstream.

Guest GPR values are live in the hardware GPRs at VM-exit. Do not leave any guest values in hardware GPRs after the guest GPR values are saved to the vcpu_vmx structure.

This is a partial mitigation for CVE 2017-5715 and CVE 2017-5753. Specifically, it defeats the Project Zero PoC for CVE 2017-5715.

Suggested-by Eric Northup <[email protected]>
Signed-off-by Jim Mattson <[email protected]>
Reviewed-by Eric Northup <[email protected]>
Reviewed-by Benjamin Serebrin <[email protected]>
Reviewed-by Andrew Honig <[email protected]>
[Paolo: Add AMD bits, Signed-off-by: Tom Lendacky <[email protected]>]
Signed-off-by Paolo Bonzini <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 arch/x86/kvm/svm.c |   19 +++++++++++++++++++
 arch/x86/kvm/vmx.c |   14 +++++++++++++-
 2 files changed, 32 insertions(+), 1 deletion(-)
arch/x86/kvm/svm.c +19 -0
@@ -4965,6 +4965,25 @@ static void svm_vcpu_run(struct kvm_vcpu
 		"mov %%r14, %c[r14](%[svm]) \n\t"
 		"mov %%r15, %c[r15](%[svm]) \n\t"
 #endif
+		/*
+		* Clear host registers marked as clobbered to prevent
+		* speculative use.
+		*/
+		"xor %%" _ASM_BX ", %%" _ASM_BX " \n\t"
+		"xor %%" _ASM_CX ", %%" _ASM_CX " \n\t"
+		"xor %%" _ASM_DX ", %%" _ASM_DX " \n\t"
+		"xor %%" _ASM_SI ", %%" _ASM_SI " \n\t"
+		"xor %%" _ASM_DI ", %%" _ASM_DI " \n\t"
+#ifdef CONFIG_X86_64
+		"xor %%r8, %%r8 \n\t"
+		"xor %%r9, %%r9 \n\t"
+		"xor %%r10, %%r10 \n\t"
+		"xor %%r11, %%r11 \n\t"
+		"xor %%r12, %%r12 \n\t"
+		"xor %%r13, %%r13 \n\t"
+		"xor %%r14, %%r14 \n\t"
+		"xor %%r15, %%r15 \n\t"
+#endif
 		"pop %%" _ASM_BP
 		:
 		: [svm]"a"(svm),
arch/x86/kvm/vmx.c +13 -1
@@ -9405,6 +9405,7 @@ static void __noclone vmx_vcpu_run(struc
 		/* Save guest registers, load host registers, keep flags */
 		"mov %0, %c[wordsize](%%" _ASM_SP ") \n\t"
 		"pop %0 \n\t"
+		"setbe %c[fail](%0)\n\t"
 		"mov %%" _ASM_AX ", %c[rax](%0) \n\t"
 		"mov %%" _ASM_BX ", %c[rbx](%0) \n\t"
 		__ASM_SIZE(pop) " %c[rcx](%0) \n\t"

@@ -9421,12 +9422,23 @@ static void __noclone vmx_vcpu_run(struc
 		"mov %%r13, %c[r13](%0) \n\t"
 		"mov %%r14, %c[r14](%0) \n\t"
 		"mov %%r15, %c[r15](%0) \n\t"
+		"xor %%r8d,  %%r8d \n\t"
+		"xor %%r9d,  %%r9d \n\t"
+		"xor %%r10d, %%r10d \n\t"
+		"xor %%r11d, %%r11d \n\t"
+		"xor %%r12d, %%r12d \n\t"
+		"xor %%r13d, %%r13d \n\t"
+		"xor %%r14d, %%r14d \n\t"
+		"xor %%r15d, %%r15d \n\t"
 #endif
 		"mov %%cr2, %%" _ASM_AX "   \n\t"
 		"mov %%" _ASM_AX ", %c[cr2](%0) \n\t"
 
+		"xor %%eax, %%eax \n\t"
+		"xor %%ebx, %%ebx \n\t"
+		"xor %%esi, %%esi \n\t"
+		"xor %%edi, %%edi \n\t"
 		"pop  %%" _ASM_BP "; pop  %%" _ASM_DX " \n\t"
-		"setbe %c[fail](%0) \n\t"
 		".pushsection .rodata \n\t"
 		".global vmx_return \n\t"
 		"vmx_return: " _ASM_PTR " 2b \n\t"

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/kvm-vmx-scrub-hardware-gprs-at-vm-exit.patch