From: Nicholas Piggin <npiggin@gmail.com>
Date: Sun, 13 Aug 2017 11:33:38 +1000
Subject: KVM: PPC: Book3S HV: Fix H_REGISTER_VPA VPA size validation
Patch-mainline: v4.14-rc1
Git-commit: eaac112eac8604917bc6c39680ff67a937626a96
References: bsc#1077761

KVM currently validates the size of the VPA registered by the client
against sizeof(struct lppaca), however we align (and therefore size)
that struct to 1kB to avoid crossing a 4kB boundary in the client.

PAPR calls for sizes >= 640 bytes to be accepted. Hard code this with
a comment.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Acked-by: Alexander Graf <agraf@suse.de>
---
 arch/powerpc/kvm/book3s_hv.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -485,7 +485,13 @@
 
 	switch (subfunc) {
 	case H_VPA_REG_VPA:		/* register VPA */
-		if (len < sizeof(struct lppaca))
+		/*
+		 * The size of our lppaca is 1kB because of the way we align
+		 * it for the guest to avoid crossing a 4kB boundary. We only
+		 * use 640 bytes of the structure though, so we should accept
+		 * clients that set a size of 640.
+		 */
+		if (len < 640)
 			break;
 		vpap = &tvcpu->arch.vpa;
 		err = 0;