[added to the 4.1 stable tree] MIPS: kvm: Fix ioctl error handling.

[Sasha Levin]

From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>

This patch has been added to the 4.1 stable tree. If you have any
objections, please let us know.

===============

[ Upstream commit 887349f69f37e71e2a8bfbd743831625a0b2ff51 ]

Calling return copy_to_user(...) or return copy_from_user in an ioctl
will not do the right thing if there's a pagefault:
copy_to_user/copy_from_user return the number of bytes not copied in
this case.

Fix up kvm on mips to do
	return copy_to_user(...)) ?  -EFAULT : 0;
and
	return copy_from_user(...)) ?  -EFAULT : 0;

everywhere.

Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: James Hogan <james.hogan@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/12709/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
 arch/mips/kvm/mips.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 22ee0af..ace4ed7 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -700,7 +700,7 @@ static int kvm_mips_get_reg(struct kvm_vcpu *vcpu,
 	} else if ((reg->id & KVM_REG_SIZE_MASK) == KVM_REG_SIZE_U128) {
 		void __user *uaddr = (void __user *)(long)reg->addr;
 
-		return copy_to_user(uaddr, vs, 16);
+		return copy_to_user(uaddr, vs, 16) ? -EFAULT : 0;
 	} else {
 		return -EINVAL;
 	}
@@ -730,7 +730,7 @@ static int kvm_mips_set_reg(struct kvm_vcpu *vcpu,
 	} else if ((reg->id & KVM_REG_SIZE_MASK) == KVM_REG_SIZE_U128) {
 		void __user *uaddr = (void __user *)(long)reg->addr;
 
-		return copy_from_user(vs, uaddr, 16);
+		return copy_from_user(vs, uaddr, 16) ? -EFAULT : 0;
 	} else {
 		return -EINVAL;
 	}
-- 
2.5.0