linux-kernel - [PATCH 4.12 35/99] KVM, pkeys: do not use PKRU value in vcpu->arch.guest

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Message-Id: <20170828080457.365824476@linuxfoundation.org>
Date:   Mon, 28 Aug 2017 10:04:33 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Junkang Fu <junkang.fjk@...baba-inc.com>,
        Yang Zhang <zy107165@...baba-inc.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 4.12 35/99] KVM, pkeys: do not use PKRU value in vcpu->arch.guest_fpu.state

4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paolo Bonzini <pbonzini@...hat.com>

commit 38cfd5e3df9c4f88e76b547eee2087ee5c042ae2 upstream.

The host pkru is restored right after vcpu exit (commit 1be0e61), so
KVM_GET_XSAVE will return the host PKRU value instead.  Fix this by
using the guest PKRU explicitly in fill_xsave and load_xsave.  This
part is based on a patch by Junkang Fu.

The host PKRU data may also not match the value in vcpu->arch.guest_fpu.state,
because it could have been changed by userspace since the last time
it was saved, so skip loading it in kvm_load_guest_fpu.

Reported-by: Junkang Fu <junkang.fjk@...baba-inc.com>
Cc: Yang Zhang <zy107165@...baba-inc.com>
Fixes: 1be0e61c1f255faaeab04a390e00c8b9b9042870
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/include/asm/fpu/internal.h |    6 +++---
 arch/x86/kvm/x86.c                  |   17 ++++++++++++++---
 2 files changed, 17 insertions(+), 6 deletions(-)

--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -450,10 +450,10 @@ static inline int copy_fpregs_to_fpstate
 	return 0;
 }
 
-static inline void __copy_kernel_to_fpregs(union fpregs_state *fpstate)
+static inline void __copy_kernel_to_fpregs(union fpregs_state *fpstate, u64 mask)
 {
 	if (use_xsave()) {
-		copy_kernel_to_xregs(&fpstate->xsave, -1);
+		copy_kernel_to_xregs(&fpstate->xsave, mask);
 	} else {
 		if (use_fxsr())
 			copy_kernel_to_fxregs(&fpstate->fxsave);
@@ -477,7 +477,7 @@ static inline void copy_kernel_to_fpregs
 			: : [addr] "m" (fpstate));
 	}
 
-	__copy_kernel_to_fpregs(fpstate);
+	__copy_kernel_to_fpregs(fpstate, -1);
 }
 
 extern int copy_fpstate_to_sigframe(void __user *buf, void __user *fp, int size);
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3236,7 +3236,12 @@ static void fill_xsave(u8 *dest, struct
 			u32 size, offset, ecx, edx;
 			cpuid_count(XSTATE_CPUID, index,
 				    &size, &offset, &ecx, &edx);
-			memcpy(dest + offset, src, size);
+			if (feature == XFEATURE_MASK_PKRU)
+				memcpy(dest + offset, &vcpu->arch.pkru,
+				       sizeof(vcpu->arch.pkru));
+			else
+				memcpy(dest + offset, src, size);
+
 		}
 
 		valid -= feature;
@@ -3274,7 +3279,11 @@ static void load_xsave(struct kvm_vcpu *
 			u32 size, offset, ecx, edx;
 			cpuid_count(XSTATE_CPUID, index,
 				    &size, &offset, &ecx, &edx);
-			memcpy(dest, src + offset, size);
+			if (feature == XFEATURE_MASK_PKRU)
+				memcpy(&vcpu->arch.pkru, src + offset,
+				       sizeof(vcpu->arch.pkru));
+			else
+				memcpy(dest, src + offset, size);
 		}
 
 		valid -= feature;
@@ -7616,7 +7625,9 @@ void kvm_load_guest_fpu(struct kvm_vcpu
 	 */
 	vcpu->guest_fpu_loaded = 1;
 	__kernel_fpu_begin();
-	__copy_kernel_to_fpregs(&vcpu->arch.guest_fpu.state);
+	/* PKRU is separately restored in kvm_x86_ops->run.  */
+	__copy_kernel_to_fpregs(&vcpu->arch.guest_fpu.state,
+				~XFEATURE_MASK_PKRU);
 	trace_kvm_fpu(1);
 }