From f9cfb1910ece5b5dbedca096fc9b7c9fe4fd3c50 Mon Sep 17 00:00:00 2001 From: Alexander Potapenko Date: Tue, 30 May 2023 10:39:11 +0200 Subject: [PATCH] string: use __builtin_memcpy() in strlcpy/strlcat lib/string.c is built with -ffreestanding, which prevents the compiler from replacing certain functions with calls to their library versions. On the other hand, this also prevents Clang and GCC from instrumenting calls to memcpy() when building with KASAN, KCSAN or KMSAN: - KASAN normally replaces memcpy() with __asan_memcpy() with the additional cc-param,asan-kernel-mem-intrinsic-prefix=1; - KCSAN and KMSAN replace memcpy() with __tsan_memcpy() and __msan_memcpy() by default. To let the tools catch memory accesses from strlcpy/strlcat, replace the calls to memcpy() with __builtin_memcpy(), which KASAN, KCSAN and KMSAN are able to replace even in -ffreestanding mode. This preserves the behavior in normal builds (__builtin_memcpy() ends up being replaced with memcpy()), and does not introduce new instrumentation in unwanted places, as strlcpy/strlcat are already instrumented. Suggested-by: Marco Elver Signed-off-by: Alexander Potapenko Reviewed-by: Marco Elver Link: https://lore.kernel.org/all/20230224085942.1791837-1-elver@google.com/ Acked-by: Kees Cook Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20230530083911.1104336-1-glider@google.com --- lib/string.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/string.c b/lib/string.c index 3d55ef890106..be26623953d2 100644 --- a/lib/string.c +++ b/lib/string.c @@ -110,7 +110,7 @@ size_t strlcpy(char *dest, const char *src, size_t size) if (size) { size_t len = (ret >= size) ? size - 1 : ret; - memcpy(dest, src, len); + __builtin_memcpy(dest, src, len); dest[len] = '\0'; } return ret; @@ -260,7 +260,7 @@ size_t strlcat(char *dest, const char *src, size_t count) count -= dsize; if (len >= count) len = count-1; - memcpy(dest, src, len); + __builtin_memcpy(dest, src, len); dest[len] = 0; return res; }