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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id m11sm1742495pgn.56.2021.07.27.14.16.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jul 2021 14:16:50 -0700 (PDT) From: Kees Cook To: linux-hardening@vger.kernel.org Cc: Kees Cook , "Gustavo A. R. Silva" , Keith Packard , Greg Kroah-Hartman , Andrew Morton , linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-staging@lists.linux.dev, linux-block@vger.kernel.org, linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com Subject: [PATCH 37/64] string.h: Introduce memset_after() for wiping trailing members/padding Date: Tue, 27 Jul 2021 13:58:28 -0700 Message-Id: <20210727205855.411487-38-keescook@chromium.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210727205855.411487-1-keescook@chromium.org> References: <20210727205855.411487-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2359; h=from:subject; bh=b9cZC+rDD66z1p4TxzACgUY06GpnBkPGzRd2vUJnnzo=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBhAHOIfqyzMaVVJ7fOFmkjuM928F3ZrP6Vj5vJQu9j TGA+E1GJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYQBziAAKCRCJcvTf3G3AJvL4D/ 432CWZcCqOkVhZ6rWzVtqmSaSBdcUlSVZvNTubv+qk3MAjGXh0WePvQ/w470x2ODfGCERhFWEDFlQj 68DffRJeemD9mQNtxja/G+yKlfKQtqj2GsW7tkAYMYGdzk44ucXmoA6jnRW6vcayOBno0Ak7JtF4lG m7CwO3b7xHmECqmbPERBBHV/EFy/4S7JgLqoPni03PW1KgZDyCWqbwmB04HSW1ssZRyLMd4s3QMY1T +9uiq7oHu8jR42VT7YaiZc18izUh7AQddCZBlvqcHK6sPbsh+klX5zZS9n02ODAklfDkBGB2gb1tzk qTxXC88avclTCkPd2GBEUQEctsttYoNcK4xZ3zRj+wlfk6n2j/Aj/ysxug7cILnKKFV1GD6Yf8nsLg 2k2xEUpWUhhQ6fcZqBd7cBs5gIDYK2zreDrTKcqVFSQ0lX6w9ZyGULXQjv3ILYDHDHvd1PewBgByhA 8aurJtfihL4zDAjHyVugkZ+nfaAmQVaovogYrWCCXoxbMKSIxExx4nWszpvOPpR1mX+l7gYP24rMp1 l768YtsiX/jU5xOMRn5iJGLFogebnye0HYfk45A60bKdiGZmynlnz5gGZL9zYD/aSJOhSfF3kz5hcE XG0Q1qnKtvYm975U6RI0dZPUWK34kAgIzA9fINgzTL6Q+FxQr5sF43MKxRyQ== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A common idiom in kernel code is to wipe the contents of a structure after a given member. This includes places where there is trailing struct padding. These open-coded cases are usually difficult to read and very sensitive to struct layout changes. Introduce a new helper, memset_after() that takes the target struct instance, the byte to write, and the member name after which the zeroing should start. Signed-off-by: Kees Cook --- include/linux/string.h | 12 ++++++++++++ lib/test_memcpy.c | 12 ++++++++++++ 2 files changed, 24 insertions(+) diff --git a/include/linux/string.h b/include/linux/string.h index cbe889e404e2..4f9f67505f70 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -272,6 +272,18 @@ static __always_inline void memcpy_and_pad(void *dest, size_t dest_len, memcpy(dest, src, dest_len); } +/** + * memset_after - Set a value after a struct member to the end of a struct + * + * @obj: Address of target struct instance + * @v: Byte value to repeatedly write + * @member: after which struct member to start writing bytes + */ +#define memset_after(obj, v, member) do { \ + memset((u8 *)(obj) + offsetofend(typeof(*(obj)), member), v, \ + sizeof(*(obj)) - offsetofend(typeof(*(obj)), member)); \ +} while (0) + /** * str_has_prefix - Test if a string has a given prefix * @str: The string to test diff --git a/lib/test_memcpy.c b/lib/test_memcpy.c index 7c64120a68a9..f52b284f4410 100644 --- a/lib/test_memcpy.c +++ b/lib/test_memcpy.c @@ -223,6 +223,13 @@ static int __init test_memset(void) 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, }, }; + struct some_bytes after = { + .data = { 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x72, + 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, + 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, + 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, + }, + }; struct some_bytes dest = { }; int count, value; u8 *ptr; @@ -254,6 +261,11 @@ static int __init test_memset(void) memset(ptr++, value++, count++); compare("argument side-effects", dest, three); + /* Verify memset_after() */ + dest = control; + memset_after(&dest, 0x72, three); + compare("memset_after()", dest, after); + return 0; #undef TEST_OP } -- 2.30.2 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=-16.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 828BDC4338F for ; Tue, 27 Jul 2021 21:16:52 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5028060BD3 for ; Tue, 27 Jul 2021 21:16:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 5028060BD3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C64D16E9DD; Tue, 27 Jul 2021 21:16:51 +0000 (UTC) Received: from mail-pl1-x62f.google.com (mail-pl1-x62f.google.com [IPv6:2607:f8b0:4864:20::62f]) by gabe.freedesktop.org (Postfix) with ESMTPS id 44D4C6E9DD for ; Tue, 27 Jul 2021 21:16:51 +0000 (UTC) Received: by mail-pl1-x62f.google.com with SMTP id k1so14618plt.12 for ; Tue, 27 Jul 2021 14:16:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=w4Fdwl9HiFMZ+llOdhUBfZSYAz9VTvRZ/zqP2rqnbdI=; b=OubzHKZ8rQkxISQj3tvDfVhvRaRW388it7d5HkY7TCu/bBaa8Pr8HfYZFrPrOiunFF 6bCQMEiL+lVzAM6jCwQcLzTiImmq8ntJYj7aynk5kXTfEehuycCEDZIeJcO5eJpfZQKn hq2FyEBWz+GBZM7N+a3OD/2asYrrsHtNzmSN0= 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=w4Fdwl9HiFMZ+llOdhUBfZSYAz9VTvRZ/zqP2rqnbdI=; b=bUj3CVLy/qNTy873fzlzCBI6kN0ByeAdNYlAeODteqr9MYRlw6reZWgsbmnsbw1uvw PTvxlMZCyxTjiwZNmA60oGV77PTbPzsY6esQW3uWbQZo+9O0kyNWJy0g1XGVQdu7hq5D 4J67GpyGFUmeyB9bF4bCYIVxKxAWAqwdqE/lHPHmNW3DhOUkPWWy7SbubVL5HjOSKcQ7 nU/rTvPCqTC4SZMLVCJg6FBEl13/nVhXRlk7sAw3ms3sP14zDEgYM7s60oaVazI9ftz+ 3WThwNuGksZ/SpkXARM+CB4XNmJ6HmRT9UPMV6loYepB6C9FrRdlNRGyA6y4cD/tEn/P gLAg== X-Gm-Message-State: AOAM5335E1ZNmbhLgGD5GeDnqRW2vgI1uWFmTvc+hpzHlon9wokolP7M Eph652V7V5e+Twx7sj5bZeR+6g== X-Google-Smtp-Source: ABdhPJzBdsmV+2iswoqD8g+SAJNwVreAx8UwnGfV68SrU1eBmBrhzMiv9tA9zD/XN/ReoAPLtd1HsQ== X-Received: by 2002:aa7:9a07:0:b029:329:46d2:c6e4 with SMTP id w7-20020aa79a070000b029032946d2c6e4mr25255299pfj.81.1627420610912; Tue, 27 Jul 2021 14:16:50 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id m11sm1742495pgn.56.2021.07.27.14.16.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jul 2021 14:16:50 -0700 (PDT) From: Kees Cook To: linux-hardening@vger.kernel.org Subject: [PATCH 37/64] string.h: Introduce memset_after() for wiping trailing members/padding Date: Tue, 27 Jul 2021 13:58:28 -0700 Message-Id: <20210727205855.411487-38-keescook@chromium.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210727205855.411487-1-keescook@chromium.org> References: <20210727205855.411487-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2359; h=from:subject; bh=b9cZC+rDD66z1p4TxzACgUY06GpnBkPGzRd2vUJnnzo=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBhAHOIfqyzMaVVJ7fOFmkjuM928F3ZrP6Vj5vJQu9j TGA+E1GJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYQBziAAKCRCJcvTf3G3AJvL4D/ 432CWZcCqOkVhZ6rWzVtqmSaSBdcUlSVZvNTubv+qk3MAjGXh0WePvQ/w470x2ODfGCERhFWEDFlQj 68DffRJeemD9mQNtxja/G+yKlfKQtqj2GsW7tkAYMYGdzk44ucXmoA6jnRW6vcayOBno0Ak7JtF4lG m7CwO3b7xHmECqmbPERBBHV/EFy/4S7JgLqoPni03PW1KgZDyCWqbwmB04HSW1ssZRyLMd4s3QMY1T +9uiq7oHu8jR42VT7YaiZc18izUh7AQddCZBlvqcHK6sPbsh+klX5zZS9n02ODAklfDkBGB2gb1tzk qTxXC88avclTCkPd2GBEUQEctsttYoNcK4xZ3zRj+wlfk6n2j/Aj/ysxug7cILnKKFV1GD6Yf8nsLg 2k2xEUpWUhhQ6fcZqBd7cBs5gIDYK2zreDrTKcqVFSQ0lX6w9ZyGULXQjv3ILYDHDHvd1PewBgByhA 8aurJtfihL4zDAjHyVugkZ+nfaAmQVaovogYrWCCXoxbMKSIxExx4nWszpvOPpR1mX+l7gYP24rMp1 l768YtsiX/jU5xOMRn5iJGLFogebnye0HYfk45A60bKdiGZmynlnz5gGZL9zYD/aSJOhSfF3kz5hcE XG0Q1qnKtvYm975U6RI0dZPUWK34kAgIzA9fINgzTL6Q+FxQr5sF43MKxRyQ== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kees Cook , linux-kbuild@vger.kernel.org, Greg Kroah-Hartman , linux-staging@lists.linux.dev, linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, "Gustavo A. R. Silva" , linux-block@vger.kernel.org, clang-built-linux@googlegroups.com, Keith Packard , netdev@vger.kernel.org, Andrew Morton Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" A common idiom in kernel code is to wipe the contents of a structure after a given member. This includes places where there is trailing struct padding. These open-coded cases are usually difficult to read and very sensitive to struct layout changes. Introduce a new helper, memset_after() that takes the target struct instance, the byte to write, and the member name after which the zeroing should start. Signed-off-by: Kees Cook --- include/linux/string.h | 12 ++++++++++++ lib/test_memcpy.c | 12 ++++++++++++ 2 files changed, 24 insertions(+) diff --git a/include/linux/string.h b/include/linux/string.h index cbe889e404e2..4f9f67505f70 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -272,6 +272,18 @@ static __always_inline void memcpy_and_pad(void *dest, size_t dest_len, memcpy(dest, src, dest_len); } +/** + * memset_after - Set a value after a struct member to the end of a struct + * + * @obj: Address of target struct instance + * @v: Byte value to repeatedly write + * @member: after which struct member to start writing bytes + */ +#define memset_after(obj, v, member) do { \ + memset((u8 *)(obj) + offsetofend(typeof(*(obj)), member), v, \ + sizeof(*(obj)) - offsetofend(typeof(*(obj)), member)); \ +} while (0) + /** * str_has_prefix - Test if a string has a given prefix * @str: The string to test diff --git a/lib/test_memcpy.c b/lib/test_memcpy.c index 7c64120a68a9..f52b284f4410 100644 --- a/lib/test_memcpy.c +++ b/lib/test_memcpy.c @@ -223,6 +223,13 @@ static int __init test_memset(void) 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, }, }; + struct some_bytes after = { + .data = { 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x72, + 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, + 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, + 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, 0x72, + }, + }; struct some_bytes dest = { }; int count, value; u8 *ptr; @@ -254,6 +261,11 @@ static int __init test_memset(void) memset(ptr++, value++, count++); compare("argument side-effects", dest, three); + /* Verify memset_after() */ + dest = control; + memset_after(&dest, 0x72, three); + compare("memset_after()", dest, after); + return 0; #undef TEST_OP } -- 2.30.2