[PATCH 2/3] KVM: fix segment_base() error checking.

[Gleb Natapov <gleb@redhat.com>]

fix segment_base() to properly check for null segment selector and
avoid accessing NULL pointer if ldt selector in null.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
---
 arch/x86/kvm/x86.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 558eb9a..49f5c7b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -229,7 +229,7 @@ unsigned long segment_base(u16 selector)
 	unsigned long table_base;
 	unsigned long v;
 
-	if (selector == 0)
+	if (!(selector & ~3))
 		return 0;
 
 	native_store_gdt(&gdt);
@@ -238,6 +238,8 @@ unsigned long segment_base(u16 selector)
 	if (selector & 4) {           /* from ldt */
 		u16 ldt_selector = kvm_read_ldt();
 
+		if (!(ldt_selector & ~3))
+			return 0;
 		table_base = segment_base(ldt_selector);
 	}
 	d = (struct desc_struct *)(table_base + (selector & ~7));
-- 
1.6.5