From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B1DBEC6FA82 for ; Tue, 13 Sep 2022 14:45:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232086AbiIMOpt (ORCPT ); Tue, 13 Sep 2022 10:45:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59690 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230195AbiIMOn0 (ORCPT ); Tue, 13 Sep 2022 10:43:26 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5763C6E2E6; Tue, 13 Sep 2022 07:22:46 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 1FE27B80FB5; Tue, 13 Sep 2022 14:22:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73081C433D6; Tue, 13 Sep 2022 14:22:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1663078960; bh=Up5LIPEXCaJUkhECqjxA40RtxLThQNHaLN4RmbE2LX4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Bkfsz6ioLigoFxjy/ImqjCAWwvdjZ1sR/KF5612FzGKR1hVDTP/J5OwWmPPVprqqX 5PlRK/LsYEpg8qSvIUgihC0nt0y2/nmR03ebwZItK5BTZof9v919fgUfsgrco6Qkaf c7QFU4YTLuiqfT9cY/IQ+YrtMD+n6++SyHIYn1iw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Marth , Ard Biesheuvel , Kees Cook Subject: [PATCH 5.10 05/79] efi: libstub: Disable struct randomization Date: Tue, 13 Sep 2022 16:04:10 +0200 Message-Id: <20220913140350.545417134@linuxfoundation.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220913140350.291927556@linuxfoundation.org> References: <20220913140350.291927556@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ard Biesheuvel commit 1a3887924a7e6edd331be76da7bf4c1e8eab4b1e upstream. The EFI stub is a wrapper around the core kernel that makes it look like a EFI compatible PE/COFF application to the EFI firmware. EFI applications run on top of the EFI runtime, which is heavily based on so-called protocols, which are struct types consisting [mostly] of function pointer members that are instantiated and recorded in a protocol database. These structs look like the ideal randomization candidates to the randstruct plugin (as they only carry function pointers), but of course, these protocols are contracts between the firmware that exposes them, and the EFI applications (including our stubbed kernel) that invoke them. This means that struct randomization for EFI protocols is not a great idea, and given that the stub shares very little data with the core kernel that is represented as a randomizable struct, we're better off just disabling it completely here. Cc: # v4.14+ Reported-by: Daniel Marth Tested-by: Daniel Marth Signed-off-by: Ard Biesheuvel Acked-by: Kees Cook Signed-off-by: Greg Kroah-Hartman --- drivers/firmware/efi/libstub/Makefile | 7 +++++++ 1 file changed, 7 insertions(+) --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -37,6 +37,13 @@ KBUILD_CFLAGS := $(cflags-y) -Os -DDIS $(call cc-option,-fno-addrsig) \ -D__DISABLE_EXPORTS +# +# struct randomization only makes sense for Linux internal types, which the EFI +# stub code never touches, so let's turn off struct randomization for the stub +# altogether +# +KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS)) + # remove SCS flags from all objects in this directory KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))