4.8-stable review patch. If anyone has any objections, please let me know.
------------------ From: Owen Hofmann <[email protected]> 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: <[email protected]> Signed-off-by: Owen Hofmann <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- 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 @@ -5045,7 +5045,7 @@ 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);
