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Commit d9092f52 authored by Owen Hofmann's avatar Owen Hofmann Committed by Paolo Bonzini
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kvm: x86: Check memopp before dereference (CVE-2016-8630) 



Commit 41061cdb ("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: 41061cdb
Message-Id: <1477592752-126650-2-git-send-email-osh@google.com>
Signed-off-by: default avatarOwen Hofmann <osh@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 355f4fb1

arch/x86/kvm/emulate.c

+1 −1
Original line number Diff line number Diff line
@@ -5045,7 +5045,7 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len) 
	/* 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);