From patchwork Thu Feb 6 18:11:29 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 13963415 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 36F4919ADB0; Thu, 6 Feb 2025 18:11:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738865494; cv=none; b=k5NDr7lH6/mVgcBfOwM+mEJmcZBFexqgoO5B9O3hYYhMM6RvpsokuevGs6QeF+Ll5s7XUhz3lN4gDj+l/TEofoMQGnWEpmlCf1yYk01ddF8+EW641CSXXeHfjxsE4LmXAYMZPP99KFKB4QRWJDMQJ3sc/sct48YB9HzeOPHrsDo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738865494; c=relaxed/simple; bh=HPvFfUBydyi8hNJ/KZN7Ew2hJ0umQS6wowFoOrda14s=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=R1wU2b8ILfMaqZ2C2Dl/9iKVac/V9CQ6OWhmuLRkskkRjfXgOPmzNgYvxdPdujy0F5Bp9ULqrbP6gu80ZkiYJJ5lNOrt02JLRCBdYPqnfWe9ApU2KrOzDg87hOjLosZbdYlmfx0/SZIQnvTGg76ykyItvGbu0vB25NNjk7qgVRw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HJ6bYnF3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HJ6bYnF3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AED62C4AF0B; Thu, 6 Feb 2025 18:11:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738865493; bh=HPvFfUBydyi8hNJ/KZN7Ew2hJ0umQS6wowFoOrda14s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HJ6bYnF3MA511vzkCs/j+C+CGkjxVQLiJERqM6oCzKMaFTKxunvO/XCRwAI4fvJsl IGjGs06oWTV4gpDrDWB+SrRZxX1SNXTC6PU9GFYNBKOn2i2g1AuG6DfhDaOdz73bqR 9MGzjuQnJqCJ4sn238/34GX2bBrrlvtUi/quXRcuzAa0FGriXJPDArNDR07pO3WP0C F7t7zJ9PVJOV02htfV7fjImpngzwJaf26c8VlLWGjpCRRgOQANhqopHSl1PN3rKrEy 04HViZMSeXUk/jhtuqW4edD/qY/7gt9J2xuxXiuNW/amPNqEbzdwvMpb68zhBGP6VX IUChdpFTSNpJA== From: Kees Cook To: Suren Baghdasaryan Cc: Kees Cook , Kent Overstreet , Andy Shevchenko , Luc Van Oostenryck , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Philipp Reisner , Miguel Ojeda , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, llvm@lists.linux.dev Subject: [PATCH 2/3] compiler.h: Introduce __must_be_char_array() Date: Thu, 6 Feb 2025 10:11:29 -0800 Message-Id: <20250206181133.3450635-2-kees@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250206175216.work.225-kees@kernel.org> References: <20250206175216.work.225-kees@kernel.org> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1222; i=kees@kernel.org; h=from:subject; bh=HPvFfUBydyi8hNJ/KZN7Ew2hJ0umQS6wowFoOrda14s=; b=owGbwMvMwCVmps19z/KJym7G02pJDOlLfgeqLhVK3791gfLfUqGPD99MO3Cu5en3bs65v1mML rZwuydldpSyMIhxMciKKbIE2bnHuXi8bQ93n6sIM4eVCWQIAxenAEykZS7Df5dGyeBryS9Mr8w9 36Obznv8SPDf/d4SxlvkeQsXvOqoesrwh4PnRMuqQwXWlhsuFs0tX8SgP9P30qFWpcAn/7Wv+7x cxgkA X-Developer-Key: i=kees@kernel.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 In preparation for adding stricter type checking to the str/mem*() helpers, provide a way to check that a variable is a character array via __must_be_char_array(). Signed-off-by: Kees Cook --- include/linux/compiler.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 7af999a131cb..a577fe0b1f8a 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -221,7 +221,13 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, #endif /* __CHECKER__ */ /* &a[0] degrades to a pointer: a different type from an array */ -#define __must_be_array(a) __BUILD_BUG_ON_ZERO_MSG(__same_type((a), &(a)[0]), "must be array") +#define __is_array(a) (!__same_type((a), &(a)[0])) +#define __must_be_array(a) __BUILD_BUG_ON_ZERO_MSG(!__is_array(a), \ + "must be array") + +#define __is_char_array(a) (__is_array(a) && sizeof((a)[0]) == 1) +#define __must_be_char_array(a) __BUILD_BUG_ON_ZERO_MSG(!__is_char_array(a), \ + "must be byte array") /* Require C Strings (i.e. NUL-terminated) lack the "nonstring" attribute. */ #define __must_be_cstr(p) \