tree c0bf158b81e425eeb159a12dd173a421cf7ddef1
parent b3a9e3b9622ae10064826dccb4f7a52bd88c7407
author Gustavo A. R. Silva <gustavoars@kernel.org> 1591665753 -0500
committer Kees Cook <keescook@chromium.org> 1592365508 -0700

overflow.h: Add flex_array_size() helper

Add flex_array_size() helper for the calculation of the size, in bytes,
of a flexible array member contained within an enclosing structure.

Example of usage:

struct something {
	size_t count;
	struct foo items[];
};

struct something *instance;

instance = kmalloc(struct_size(instance, items, count), GFP_KERNEL);
instance->count = count;
memcpy(instance->items, src, flex_array_size(instance, items, instance->count));

The helper returns SIZE_MAX on overflow instead of wrapping around.

Additionally replaces parameter "n" with "count" in struct_size() helper
for greater clarity and unification.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20200609012233.GA3371@embeddedor
Signed-off-by: Kees Cook <keescook@chromium.org>