From patchwork Wed Jan 19 09:31:09 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 533892 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 1F84BC433FE for ; Wed, 19 Jan 2022 09:31:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239791AbiASJb0 (ORCPT ); Wed, 19 Jan 2022 04:31:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234544AbiASJbY (ORCPT ); Wed, 19 Jan 2022 04:31:24 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 76E5CC061574 for ; Wed, 19 Jan 2022 01:31:23 -0800 (PST) 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 sin.source.kernel.org (Postfix) with ESMTPS id 2898ACE1C49 for ; Wed, 19 Jan 2022 09:31:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3AEC0C004E1; Wed, 19 Jan 2022 09:31:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1642584679; bh=L2q8bGntulfdCDWGccXI5D0JvkDEk1cC3vPfOr9fYpA=; h=From:To:Cc:Subject:Date:From; b=hls1iYF14LXQcfzfqJhHkAzg92H03fNLJpkZGuLqJSoWdYsxjT0wQaUoULSyIGBMC jiGQfHanhgMhoCh0SiuAFN9sQ85hZPaL1WPkvv6jwI12jipwQaW+5s6GRXHoEWAH1P GxWuNi/u9baog7sAbEooK046d2ILMu4cRws8x1Ab5C5dK0qMy5x4FZ/DVnuOPNboXy cVHxK37fvY5Qy/KnZoRKjGTWN2RSHj5zo0dP/5zkfgZg/BK6QjB9xpTSe4FBUWw1zW LlNqmoeOOTnVDCNlFPXVPXB2xFnimTZjHWrSiPQBFgmovmMRceBSzJaf1I5BJbfLe3 RKig1s7zC+e1g== From: Ard Biesheuvel To: linux-crypto@vger.kernel.org Cc: herbert@gondor.apana.org.au, arnd@arndb.de, Ard Biesheuvel Subject: [PATCH] crypto: memneq: avoid implicit unaligned accesses Date: Wed, 19 Jan 2022 10:31:09 +0100 Message-Id: <20220119093109.1567314-1-ardb@kernel.org> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3133; h=from:subject; bh=L2q8bGntulfdCDWGccXI5D0JvkDEk1cC3vPfOr9fYpA=; b=owEB7QES/pANAwAKAcNPIjmS2Y8kAcsmYgBh59pcB5eSl79xvFUSF+AuHsu53O4ancFJK7p0Z3O9 63XgjhmJAbMEAAEKAB0WIQT72WJ8QGnJQhU3VynDTyI5ktmPJAUCYefaXAAKCRDDTyI5ktmPJFJZDA C5/NvH58dh2fXfjrRbiC4Y8ju4vnjD1Fm/VKdGofdIo2ntgV+uPVYCBaf7Ui+WDtDs6GP+o9nTjW9p hh2HbBAGy7kIebLacvb5JYGsrkZuOIML3dbqmv6w1pUJ7qf4XtaIgqmcNoRHsr9bR/yJrOQEt3+tc9 b24Sno3pAy+NN/Rm222pVX2dvLjWlimv+jk5cOwQqQWCRiO7l2IFoR5BswQFBUckHIaX7zK4NessJr s/ELtAlLGBzUiX3sSeiSQztqd9Z4vwOaFUExDtgvQg0lWCWb5cKakHDJV486nYV2rZpZNIiTo4qfg6 mPHg0BJLMWOBx8EfzSCeKBAeRWMnwSgwGW2wyZn4+6lZTxQJenswq92yctY7VQ34ByOp3UV6srYUaI 3AKWWppxuRSbspw8qVEywRODTQT5+EMbJLEMZJnixzE8LtNy2Z9qVDZpUdCOgTOHPPwvSs74W/p6D2 FIFy71Bfpi0Zy9tloS4uMphh040QaIUNR3pW9IH9ot7FU= X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org The C standard does not support dereferencing pointers that are not aligned with respect to the pointed-to type, and doing so is technically undefined behavior, even if the underlying hardware supports it. This means that conditionally dereferencing such pointers based on whether CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y is not the right thing to do, and actually results in alignment faults on ARM, which are fixed up on a slow path. Instead, we should use the unaligned accessors in such cases: on architectures that don't care about alignment, they will result in identical codegen whereas, e.g., codegen on ARM will avoid doubleword loads and stores but use ordinary ones, which are able to tolerate misalignment. Link: https://lore.kernel.org/linux-crypto/CAHk-=wiKkdYLY0bv+nXrcJz3NH9mAqPAafX7PpW5EwVtxsEu7Q@mail.gmail.com/ Signed-off-by: Ard Biesheuvel Reviewed-by: Eric Biggers --- crypto/memneq.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) diff --git a/crypto/memneq.c b/crypto/memneq.c index afed1bd16aee..fb11608b1ec1 100644 --- a/crypto/memneq.c +++ b/crypto/memneq.c @@ -60,6 +60,7 @@ */ #include +#include #ifndef __HAVE_ARCH_CRYPTO_MEMNEQ @@ -71,7 +72,8 @@ __crypto_memneq_generic(const void *a, const void *b, size_t size) #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) while (size >= sizeof(unsigned long)) { - neq |= *(unsigned long *)a ^ *(unsigned long *)b; + neq |= get_unaligned((unsigned long *)a) ^ + get_unaligned((unsigned long *)b); OPTIMIZER_HIDE_VAR(neq); a += sizeof(unsigned long); b += sizeof(unsigned long); @@ -95,18 +97,24 @@ static inline unsigned long __crypto_memneq_16(const void *a, const void *b) #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS if (sizeof(unsigned long) == 8) { - neq |= *(unsigned long *)(a) ^ *(unsigned long *)(b); + neq |= get_unaligned((unsigned long *)a) ^ + get_unaligned((unsigned long *)b); OPTIMIZER_HIDE_VAR(neq); - neq |= *(unsigned long *)(a+8) ^ *(unsigned long *)(b+8); + neq |= get_unaligned((unsigned long *)(a + 8)) ^ + get_unaligned((unsigned long *)(b + 8)); OPTIMIZER_HIDE_VAR(neq); } else if (sizeof(unsigned int) == 4) { - neq |= *(unsigned int *)(a) ^ *(unsigned int *)(b); + neq |= get_unaligned((unsigned int *)a) ^ + get_unaligned((unsigned int *)b); OPTIMIZER_HIDE_VAR(neq); - neq |= *(unsigned int *)(a+4) ^ *(unsigned int *)(b+4); + neq |= get_unaligned((unsigned int *)(a + 4)) ^ + get_unaligned((unsigned int *)(b + 4)); OPTIMIZER_HIDE_VAR(neq); - neq |= *(unsigned int *)(a+8) ^ *(unsigned int *)(b+8); + neq |= get_unaligned((unsigned int *)(a + 8)) ^ + get_unaligned((unsigned int *)(b + 8)); OPTIMIZER_HIDE_VAR(neq); - neq |= *(unsigned int *)(a+12) ^ *(unsigned int *)(b+12); + neq |= get_unaligned((unsigned int *)(a + 12)) ^ + get_unaligned((unsigned int *)(b + 12)); OPTIMIZER_HIDE_VAR(neq); } else #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */