4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Owen Hofmann <o...@google.com>
commit d9092f52d7e61dd1557f2db2400ddb430e85937e upstream.
Commit 41061cdb98 ("KVM: emulate: do not initialize memopp") removes a
check for non-NULL under incorrect assumptions. An undefined instruction
with a ModR/M byte with Mod=0 and R/M-5 (e.g. 0xc7 0x15) will attempt
to dereference a null pointer here.
Fixes: 41061cdb98a0bec464278b4db8e894a3121671f5
Message-Id: <1477592752-126650-2-git-send-email-...@google.com>
Signed-off-by: Owen Hofmann <o...@google.com>
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
arch/x86/kvm/emulate.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5033,7 +5033,7 @@ done_prefixes:
/* Decode and fetch the destination operand: register or memory. */
rc = decode_operand(ctxt, &ctxt->dst, (ctxt->d >> DstShift) & OpMask);
- if (ctxt->rip_relative)
+ if (ctxt->rip_relative && likely(ctxt->memopp))
ctxt->memopp->addr.mem.ea = address_mask(ctxt,
ctxt->memopp->addr.mem.ea + ctxt->_eip);
