Re: [PATCH 4/6] string: Add __realloc_size hint to kmemdup()

[Rasmus Villemoes]

On 01/11/2022 23.33, Kees Cook wrote:
> Add __realloc_size() hint to kmemdup() so the compiler can reason about
> the length of the returned buffer. (These must not use __alloc_size,
> since those include __malloc which says the contents aren't defined[1]).
> 
> [1] https://lore.kernel.org/linux-hardening/d199c2af-06af-8a50-a6a1-00eefa0b67b4@xxxxxxxxx/
> 

>  extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
> -extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __alloc_size(2);
> +extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2);

What tree is this based on? I see that kmemdup() has grown that bogus
__alloc_size in next-20221101, but in next-20221102 this commit seems to
DTRT, namely

-extern void *kmemdup(const void *src, size_t len, gfp_t gfp);
+extern void *kmemdup(const void *src, size_t len, gfp_t gfp)
__realloc_size(2);

(i.e. there should never be an intermediate commit where kmemdup has
__alloc_size()).

Rasmus