From 9a93048476e7cbdde00cdeebe66b6504995eac92 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Wed, 16 Apr 2025 10:29:15 -0700 Subject: [PATCH] overflow: Clarify expectations for getting DEFINE_FLEX variable sizes Mention the use of __member_size() for DEFINE_FLEX variables as a hint for getting at the compile-time size of the resulting flexible array member. Reviewed-by: Gustavo A. R. Silva Link: https://lore.kernel.org/r/20250416172911.work.854-kees@kernel.org Signed-off-by: Kees Cook --- include/linux/overflow.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/include/linux/overflow.h b/include/linux/overflow.h index 0c7e3dcfe867..6ee67c20b575 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -419,6 +419,7 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend) * Define a zeroed, on-stack, instance of @type structure with a trailing * flexible array member. * Use __struct_size(@name) to get compile-time size of it afterwards. + * Use __member_size(@name->member) to get compile-time size of @name members. */ #define DEFINE_RAW_FLEX(type, name, member, count) \ _DEFINE_FLEX(type, name, member, count, = {}) @@ -436,6 +437,7 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend) * Define a zeroed, on-stack, instance of @TYPE structure with a trailing * flexible array member. * Use __struct_size(@NAME) to get compile-time size of it afterwards. + * Use __member_size(@NAME->member) to get compile-time size of @NAME members. */ #define DEFINE_FLEX(TYPE, NAME, MEMBER, COUNTER, COUNT) \ _DEFINE_FLEX(TYPE, NAME, MEMBER, COUNT, = { .obj.COUNTER = COUNT, }) -- 2.25.1