Messages in this thread | | | From | "Gustavo A. R. Silva" <> | Subject | Re: [PATCH v2] overflow.h: Add flex_array_size() helper | Date | Tue, 16 Jun 2020 15:48:51 -0500 |
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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 <keescook@chromium.org> > > (I wonder who's tree this should go via?) >
Yours? :)
> -Kees > > [1] https://lore.kernel.org/lkml/20180507113902.GC18116@bombadil.infradead.org/ > [2] https://lore.kernel.org/lkml/CA+55aFy8DSRoUvtiuu5w+XGOK6tYvtJGBH-i8i-y7aiUD2EGLA@mail.gmail.com/ >
-- Gustavo
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