KVM: emulator: Fix permission checking in io permission bitmap
Currently if io port + len crosses 8bit boundary in io permission bitmap the
check may allow IO that otherwise should not be allowed. The patch fixes that.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index d6088b8..0ad47b8 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1769,8 +1769,7 @@
struct desc_struct tr_seg;
u32 base3;
int r;
- u16 io_bitmap_ptr;
- u8 perm, bit_idx = port & 0x7;
+ u16 io_bitmap_ptr, perm, bit_idx = port & 0x7;
unsigned mask = (1 << len) - 1;
unsigned long base;
@@ -1788,7 +1787,7 @@
return false;
if (io_bitmap_ptr + port/8 > desc_limit_scaled(&tr_seg))
return false;
- r = ops->read_std(base + io_bitmap_ptr + port/8, &perm, 1, ctxt->vcpu,
+ r = ops->read_std(base + io_bitmap_ptr + port/8, &perm, 2, ctxt->vcpu,
NULL);
if (r != X86EMUL_CONTINUE)
return false;