linux-kernel - [PATCH 4.7 063/184] KVM: s390: dont use current->thread.fpu.* when accessing registers

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Date:   Thu, 22 Sep 2016 19:39:57 +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, Hao QingFeng <haoqf@...ux.vnet.ibm.com>,
        David Hildenbrand <dahi@...ux.vnet.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>
Subject: [PATCH 4.7 063/184] KVM: s390: dont use current->thread.fpu.* when accessing registers

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

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

From: David Hildenbrand <dahi@...ux.vnet.ibm.com>

commit a7d4b8f2565ad0dfdff9a222d1d87990c73b36e8 upstream.

As the meaning of these variables and pointers seems to change more
frequently, let's directly access our save area, instead of going via
current->thread.

Right now, this is broken for set/get_fpu. They simply overwrite the
host registers, as the pointers to the current save area were turned
into the static host save area.

Fixes: 3f6813b9a5e0 ("s390/fpu: allocate 'struct fpu' with the task_struct")
Reported-by: Hao QingFeng <haoqf@...ux.vnet.ibm.com>
Signed-off-by: David Hildenbrand <dahi@...ux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/s390/kvm/kvm-s390.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1951,9 +1951,10 @@ int kvm_arch_vcpu_ioctl_set_fpu(struct k
 		return -EINVAL;
 	current->thread.fpu.fpc = fpu->fpc;
 	if (MACHINE_HAS_VX)
-		convert_fp_to_vx(current->thread.fpu.vxrs, (freg_t *)fpu->fprs);
+		convert_fp_to_vx((__vector128 *) vcpu->run->s.regs.vrs,
+				 (freg_t *) fpu->fprs);
 	else
-		memcpy(current->thread.fpu.fprs, &fpu->fprs, sizeof(fpu->fprs));
+		memcpy(vcpu->run->s.regs.fprs, &fpu->fprs, sizeof(fpu->fprs));
 	return 0;
 }
 
@@ -1962,9 +1963,10 @@ int kvm_arch_vcpu_ioctl_get_fpu(struct k
 	/* make sure we have the latest values */
 	save_fpu_regs();
 	if (MACHINE_HAS_VX)
-		convert_vx_to_fp((freg_t *)fpu->fprs, current->thread.fpu.vxrs);
+		convert_vx_to_fp((freg_t *) fpu->fprs,
+				 (__vector128 *) vcpu->run->s.regs.vrs);
 	else
-		memcpy(fpu->fprs, current->thread.fpu.fprs, sizeof(fpu->fprs));
+		memcpy(fpu->fprs, vcpu->run->s.regs.fprs, sizeof(fpu->fprs));
 	fpu->fpc = current->thread.fpu.fpc;
 	return 0;
 }