From: Kees Cook Date: Wed, 16 Apr 2025 17:29:15 +0000 (-0700) Subject: overflow: Clarify expectations for getting DEFINE_FLEX variable sizes X-Git-Tag: v6.16-rc1~151^2~18 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9a93048476e7cbdde00cdeebe66b6504995eac92;p=thirdparty%2Fkernel%2Flinux.git 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 --- diff --git a/include/linux/overflow.h b/include/linux/overflow.h index 0c7e3dcfe8670..6ee67c20b575b 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, })