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 X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9CBB8C04AAE for ; Thu, 9 May 2019 03:13:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 751A42175B for ; Thu, 9 May 2019 03:13:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726698AbfEIDNG (ORCPT ); Wed, 8 May 2019 23:13:06 -0400 Received: from mx2.suse.de ([195.135.220.15]:58298 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726254AbfEIDNF (ORCPT ); Wed, 8 May 2019 23:13:05 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 9430EAD70; Thu, 9 May 2019 03:13:03 +0000 (UTC) Subject: Re: [PATCH v3 0/7] crypto: x86: Fix indirect function call casts To: Eric Biggers , Kees Cook Cc: Herbert Xu , Ingo Molnar , Thomas Gleixner , Borislav Petkov , X86 ML , linux-crypto , LKML , Kernel Hardening References: <20190507161321.34611-1-keescook@chromium.org> <20190507170039.GB1399@sol.localdomain> <20190507215045.GA7528@sol.localdomain> <20190508133606.nsrzthbad5kynavp@gondor.apana.org.au> <20190509020439.GB693@sol.localdomain> From: Joao Moreira Message-ID: <8c9a53b9-12e6-3380-21c8-4fe85342f0ac@suse.de> Date: Thu, 9 May 2019 00:12:54 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190509020439.GB693@sol.localdomain> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/8/19 11:04 PM, Eric Biggers wrote: > On Wed, May 08, 2019 at 02:08:25PM -0700, Kees Cook wrote: >> On Wed, May 8, 2019 at 6:36 AM Herbert Xu wrote: >>> On Tue, May 07, 2019 at 02:50:46PM -0700, Eric Biggers wrote: >>>> >>>> I don't know yet. It's difficult to read the code with 2 layers of macros. >>>> >>>> Hence why I asked why you didn't just change the prototypes to be compatible. >>> >>> I agree. Kees, since you're changing this anyway please make it >>> look better not worse. >> >> Do you mean I should use the typedefs in the new macros? I'm not aware >> of a way to use a typedef to declare a function body, so I had to >> repeat them. I'm open to suggestions! >> >> As far as "fixing the prototypes", the API is agnostic of the context >> type, and uses void *. And also it provides a way to call the same >> function with different pointer types on the other arguments: >> >> For example, quoting the existing code: >> >> asmlinkage void twofish_dec_blk(struct twofish_ctx *ctx, u8 *dst, >> const u8 *src); >> >> Which is used for ecb and cbc: >> >> #define GLUE_FUNC_CAST(fn) ((common_glue_func_t)(fn)) >> #define GLUE_CBC_FUNC_CAST(fn) ((common_glue_cbc_func_t)(fn)) >> ... >> static const struct common_glue_ctx twofish_dec = { >> ... >> .fn_u = { .ecb = GLUE_FUNC_CAST(twofish_dec_blk) } >> >> static const struct common_glue_ctx twofish_dec_cbc = { >> ... >> .fn_u = { .cbc = GLUE_CBC_FUNC_CAST(twofish_dec_blk) } >> >> which have different prototypes: >> >> typedef void (*common_glue_func_t)(void *ctx, u8 *dst, const u8 *src); >> typedef void (*common_glue_cbc_func_t)(void *ctx, u128 *dst, const u128 *src); >> ... >> struct common_glue_func_entry { >> unsigned int num_blocks; /* number of blocks that @fn will process */ >> union { >> common_glue_func_t ecb; >> common_glue_cbc_func_t cbc; >> common_glue_ctr_func_t ctr; >> common_glue_xts_func_t xts; >> } fn_u; >> }; >> > > As Herbert said, the ctx parameters could be made 'void *'. > This is how things were done in the original patch set, but some concerns were raised about this approach: https://lkml.org/lkml/2018/4/16/74 Tks, Joao. > And I also asked whether indirect calls to asm code are even allowed with CFI. > IIRC, the AOSP kernels have been patched to remove them from arm64. It would be > helpful if you would answer that question, since it would inform the best > approach here. > > As for the "ecb" functions taking 'u8 *' but the "cbc" ones taking 'u128 *' and > the same function being used in the blocks==1 case, you could just pick one of > the types to use for both. 'u8 *' probably makes more sense since both ecb and > cbc operate on blocks of 16 bytes but don't interpret them as 128-bit integers. > > - Eric >