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Date: Tue, 30 Aug 2022 13:53:08 -0700 From: Nick Desaulniers <ndesaulniers@...gle.com> To: Kees Cook <keescook@...omium.org> Cc: Nathan Chancellor <nathan@...nel.org>, Tom Rix <trix@...hat.com>, linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org, llvm@...ts.linux.dev, Jiri Kosina <jikos@...nel.org>, Benjamin Tissoires <benjamin.tissoires@...hat.com>, linux-input@...r.kernel.org, Masahiro Yamada <masahiroy@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com> Subject: [PATCH 2/3] fortify: cosmetic cleanups to __compiletime_strlen Two things I noticed in __compiletime_strlen: 1. A temporary, __p, is created+used to avoid repeated side effects from multiple evaluation of the macro parameter, but the macro parameter was being used accidentally in __builtin_object_size. 2. The temporary has a curious signedness and const-less qualification. Just use __auto_type. 3. (size_t)-1 is perhaps more readable as -1UL. 4. __p_size == -1UL when __builtin_object_size can't evaluate the object size at compile time. We could just reuse __ret and use one less variable here. Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com> --- include/linux/fortify-string.h | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h index c5adad596a3f..aaf73575050f 100644 --- a/include/linux/fortify-string.h +++ b/include/linux/fortify-string.h @@ -22,11 +22,10 @@ void __write_overflow_field(size_t avail, size_t wanted) __compiletime_warning(" #define __compiletime_strlen(p) \ ({ \ - unsigned char *__p = (unsigned char *)(p); \ - size_t __ret = (size_t)-1; \ - size_t __p_size = __object_size(p, 1); \ - if (__p_size != (size_t)-1) { \ - size_t __p_len = __p_size - 1; \ + __auto_type __p = (p); \ + size_t __ret = __object_size(__p, 1); \ + if (__ret != -1UL) { \ + size_t __p_len = __ret - 1; \ if (__builtin_constant_p(__p[__p_len]) && \ __p[__p_len] == '\0') \ __ret = __builtin_strlen(__p); \ -- 2.37.2.672.g94769d06f0-goog
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