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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id pf8sm3953732pjb.20.2022.02.08.14.53.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Feb 2022 14:53:53 -0800 (PST) From: Kees Cook To: Kees Cook Cc: Miguel Ojeda , Nick Desaulniers , Nathan Chancellor , George Burgess IV , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, llvm@lists.linux.dev Subject: [PATCH v7 7/8] fortify: Make sure strlen() may still be used as a constant expression Date: Tue, 8 Feb 2022 14:53:49 -0800 Message-Id: <20220208225350.1331628-8-keescook@chromium.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220208225350.1331628-1-keescook@chromium.org> References: <20220208225350.1331628-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2075; h=from:subject; bh=x0eO+QDq4SY1xj1KazbfZHej8GhFXPKxChBqWEMgyXk=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBiAvR98C7j5hKV7f7E3A2woQIyNSxiyRCxHsDAXHnD p1tjCnGJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYgL0fQAKCRCJcvTf3G3AJqUED/ 4/Uw1zXc3soNRZuOJXIGr0vVZQJi8Zs371ZIAhRPRIej8MJHKof1likyWfRx/uf4cv9zccrOpB7mwW DY5ULp9uEtD9Nh/Z4cyIkNyzDFa/p46H8h5ZVT4y3y9IcpUxMaXU2jJ00aNbNNGgCUOx9XjlBoNjM7 AxvxamkuT5MUywf5+raTMeXktKrC7VffAO1cJyaoXANfCXLs3lH5UceD6pcdzxbn+vz0aQZQhDRwMi CrWoevmY9go+zZEUw+hW4cVW8gmedWQ5RMlnWpzepT/294hza9/XVWQ0ugmewmZD3SJFFr95I+KBq0 pmGtNruHMUVHxGY2iexfwareMdWGUVradhj8JCXNFwiKLMdP54kwA3SIzeIAHE0Aa+IBW55XeWeCa8 SILOWmNX1VvxDgBGX8j9KrumiZT9/C+A6/fj8eMBZbcGn3qcrqoKIW2MFNbzY5NFgUG565yZVWBVuS COPv+WauZVejhzLU+vUQYCQ2vJa+pCyMa9yDiaFLkGNEVjdomfJSEGTez9QHoBP+iDLe5/8SOOeMMK ZJ4sYpUKufPja+UGwdx5KBwqmImWNgKF/yeM+oDdwXFeiH6MJjEp112rEYHn1bMX1l2FVej25gREpG FWj1bEtWcTrSgU19gsQPV0/++Q6E2IX6XbOiT6cdN7+NGmEdLuEfEdcem+pQ== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org In preparation for enabling Clang FORTIFY_SOURCE support, redefine strlen() as a macro that tests for being a constant expression so that strlen() can still be used in static initializers, which is lost when adding __pass_object_size and __overloadable. An example of this usage can be seen here: https://lore.kernel.org/all/202201252321.dRmWZ8wW-lkp@intel.com/ Notably, this constant expression feature of strlen() is not available for architectures that build with -ffreestanding. This means the kernel currently does not universally expect strlen() to be used this way, but since there _are_ some build configurations that depend on it, retain the characteristic for Clang FORTIFY_SOURCE builds too. Signed-off-by: Kees Cook --- include/linux/fortify-string.h | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h index db1ad1c1c79a..f77cf22e2d60 100644 --- a/include/linux/fortify-string.h +++ b/include/linux/fortify-string.h @@ -2,6 +2,8 @@ #ifndef _LINUX_FORTIFY_STRING_H_ #define _LINUX_FORTIFY_STRING_H_ +#include + #define __FORTIFY_INLINE extern __always_inline __gnu_inline #define __RENAME(x) __asm__(#x) @@ -95,9 +97,16 @@ __FORTIFY_INLINE __kernel_size_t strnlen(const char * const p, __kernel_size_t m return ret; } -/* defined after fortified strnlen to reuse it. */ +/* + * Defined after fortified strnlen to reuse it. However, it must still be + * possible for strlen() to be used on compile-time strings for use in + * static initializers (i.e. as a constant expression). + */ +#define strlen(p) \ + __builtin_choose_expr(__is_constexpr(__builtin_strlen(p)), \ + __builtin_strlen(p), __fortify_strlen(p)) __FORTIFY_INLINE __diagnose_as(__builtin_strlen, 1) -__kernel_size_t strlen(const char * const p) +__kernel_size_t __fortify_strlen(const char * const p) { __kernel_size_t ret; size_t p_size = __builtin_object_size(p, 1); -- 2.30.2