From patchwork Sun Oct 25 14:31:14 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Arvind Sankar X-Patchwork-Id: 285403 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=-12.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham 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 5F005C4363A for ; Sun, 25 Oct 2020 14:31:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 24182208E4 for ; Sun, 25 Oct 2020 14:31:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1414761AbgJYObY (ORCPT ); Sun, 25 Oct 2020 10:31:24 -0400 Received: from mail-qt1-f196.google.com ([209.85.160.196]:34851 "EHLO mail-qt1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1414677AbgJYObY (ORCPT ); Sun, 25 Oct 2020 10:31:24 -0400 Received: by mail-qt1-f196.google.com with SMTP id c15so4921116qtc.2; Sun, 25 Oct 2020 07:31:23 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=MN0s8vlWrwWpnF9v8V5eNRd1d4ATTd49nrUqABX5hio=; b=ABdQs9FVB8/FzH8dKAILE4TkU/0WO2NHBuHP9zeq4lYz1kyJ1asNrBgxWVMh3bsIUA AGWqBw/D8j0CWprixxXJBrfZn8QYylaPBG7j5JXYE1xztO5/jP7cuyVTCaJcYI7JMFet ym9MPhVf2aSjXQxLDSVp/zbA6OmTWs09RCgsd/fHdThVOn8Wk/TfeArCL3yq7DUeLGAA 54iSTNyKhgttz/geEpm2deBV/KaYlKB0zzSO8LlXDbSkAj+8uwmb/T6i1iYAXSk7Tpep gHkd4elqXb8n6A1OXl/6X0xDJzvEdITCAJ3HNCWDLn/8iHZu9arKrirb3D+wxoQwm1jV 6BRw== X-Gm-Message-State: AOAM532lF+KE9aJ4fJKsjf2EHbOqj8UbFy5WyumVkF4m0ddCexbIT5hD LG1SBDNbJW3nsw5kwcP9kpk= X-Google-Smtp-Source: ABdhPJyOKIf4i9PAJrrokcQidlOn76hVGHHE4GJVfoadKRDzionc4xHJHuexCc+Z/QteZtRrMAURNg== X-Received: by 2002:aed:3a86:: with SMTP id o6mr11818147qte.333.1603636283458; Sun, 25 Oct 2020 07:31:23 -0700 (PDT) Received: from rani.riverdale.lan ([2001:470:1f07:5f3::b55f]) by smtp.gmail.com with ESMTPSA id s73sm4740898qke.71.2020.10.25.07.31.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 25 Oct 2020 07:31:22 -0700 (PDT) From: Arvind Sankar To: Herbert Xu , "David S. Miller" , "linux-crypto@vger.kernel.org" , Eric Biggers , David Laight Cc: linux-kernel@vger.kernel.org, Eric Biggers Subject: [PATCH v4 1/6] crypto: lib/sha256 - Use memzero_explicit() for clearing state Date: Sun, 25 Oct 2020 10:31:14 -0400 Message-Id: <20201025143119.1054168-2-nivedita@alum.mit.edu> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201025143119.1054168-1-nivedita@alum.mit.edu> References: <20201025143119.1054168-1-nivedita@alum.mit.edu> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org Without the barrier_data() inside memzero_explicit(), the compiler may optimize away the state-clearing if it can tell that the state is not used afterwards. At least in lib/crypto/sha256.c:__sha256_final(), the function can get inlined into sha256(), in which case the memset is optimized away. Signed-off-by: Arvind Sankar Reviewed-by: Eric Biggers Acked-by: Ard Biesheuvel --- lib/crypto/sha256.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/crypto/sha256.c b/lib/crypto/sha256.c index 2321f6cb322f..d43bc39ab05e 100644 --- a/lib/crypto/sha256.c +++ b/lib/crypto/sha256.c @@ -265,7 +265,7 @@ static void __sha256_final(struct sha256_state *sctx, u8 *out, int digest_words) put_unaligned_be32(sctx->state[i], &dst[i]); /* Zeroize sensitive information. */ - memset(sctx, 0, sizeof(*sctx)); + memzero_explicit(sctx, sizeof(*sctx)); } void sha256_final(struct sha256_state *sctx, u8 *out)