From ac64115a66c18c01745bbd3c47a36b124e5fd8c0 Mon Sep 17 00:00:00 2001
From: Greg Kurz <groug@kaod.org>
Date: Thu, 14 Sep 2017 23:56:25 +0200
Subject: [PATCH] KVM: PPC: Fix oops when checking KVM_CAP_PPC_HTM

References: bsc#1061840
Patch-mainline: v4.14-rc7
Git-commit: ac64115a66c18c01745bbd3c47a36b124e5fd8c0
modified by merge 072df8130c6b602c8ee219f7b06394680cafad2f

The following program causes a kernel oops:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>

main()
{
    int fd = open("/dev/kvm", O_RDWR);
    ioctl(fd, KVM_CHECK_EXTENSION, KVM_CAP_PPC_HTM);
}

This happens because when using the global KVM fd with
KVM_CHECK_EXTENSION, kvm_vm_ioctl_check_extension() gets
called with a NULL kvm argument, which gets dereferenced
in is_kvmppc_hv_enabled(). Spotted while reading the code.

Let's use the hv_enabled fallback variable, like everywhere
else in this function.

Fixes: 23528bb21ee2 ("KVM: PPC: Introduce KVM_CAP_PPC_HTM")
Cc: stable@vger.kernel.org # v4.7+
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/kvm/powerpc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 291146c6cb4c..a407f1cad495 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -624,7 +624,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		break;
 #endif
 	case KVM_CAP_PPC_HTM:
-		r = is_kvmppc_hv_enabled(kvm) &&
+		r = hv_enabled &&
 		    (cur_cpu_spec->cpu_user_features2 & PPC_FEATURE2_HTM_COMP);
 		break;
 	default:
-- 
2.13.6