On Tue, Jun 16, 2020 at 03:48:51PM -0500, Gustavo A. R. Silva wrote: > > > On 6/10/20 16:38, Kees Cook wrote: > > >> -#define struct_size(p, member, n) \ > >> - __ab_c_size(n, \ > >> +#define struct_size(p, member, count) > >> \ > >> + __ab_c_size(count, > >> \ > >> sizeof(*(p)->member) + __must_be_array((p)->member),\ > >> sizeof(*(p))) > > > > I like the "count" change -- "n" can be seen as either count or bytes, > > so I like this being distinctly "count". > > > > Yep. :) > > >> > >> +/** > >> + * flex_array_size() - Calculate size, in bytes, of a flexible array > >> member > >> + * within an enclosing structure. Read on for more details. > >> + * > >> + * @p: Pointer to the structure. > >> + * @member: Name of the flexible array member. > >> + * @count: Number of elements in the array. > >> + * > >> + * Calculates size, in bytes, of a flexible array @member of @count > >> elements > >> + * within structure @p. > >> + * > >> + * Return: number of bytes needed or SIZE_MAX on overflow. > >> + */ > >> +#define flex_array_size(p, member, count) > >> \ > >> + array_size(count, > >> \ > >> + sizeof(*(p)->member) + __must_be_array((p)->member)) > >> + > >> #endif /* __LINUX_OVERFLOW_H */ > > > > I like it! You mentioned off-list that maybe this could be named > > sizeof_flex_array() (like sizeof_field(), etc), and that does seem > > attractive. As you also mentioned, it begs the question of renaming > > struct_size() to sizeof_struct(). > > > > Looking back through the thread[1], it seems the name came from Linus[2], > > and was more related to the existing array_size() helper. > > > > So, how about this, as a convention we can use to make a choice: > > > > For things that are strictly constant in size, we can use sizeof_*. For > > things that have a dynamic component, we'll use *_size(). So, this patch > > is correct as-is. > > > > I like the idea. I haven't thought it in terms of dynamic and constant size, > but it sounds sensible. > > > Acked-by: Kees Cook <keesc...@chromium.org> > > > > (I wonder who's tree this should go via?) > > > > Yours? :)
Done; I'll see if Linus will take this for -rc2 so you'll be able to use it for v5.9 patches... Thanks! -- Kees Cook
