mm/page_alloc: fix __alloc_size attribute for alloc_pages_exact_nid

The second parameter of alloc_pages_exact_nid is the one indicating the
size of memory pointed by the returned pointer.

Link: https://lkml.kernel.org/r/YbjEgwhn4bGblp//@coeus
Fixes: abd58f3 ("mm/page_alloc: add __alloc_size attributes for better bounds checking")
Signed-off-by: Thibaut Sautereau <thibaut.sautereau@ssi.gouv.fr>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Daniel Micay <danielmicay@gmail.com>
Cc: Levente Polyak <levente@leventepolyak.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: tsautereau-anssi

include/linux/gfp.h

@@ -624,7 +624,7 @@ extern unsigned long get_zeroed_page(gfp_t gfp_mask);
 
 void *alloc_pages_exact(size_t size, gfp_t gfp_mask) __alloc_size(1);
 void free_pages_exact(void *virt, size_t size);
-__meminit void *alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask) __alloc_size(1);
+__meminit void *alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask) __alloc_size(2);
 
 #define __get_free_page(gfp_mask) \
 		__get_free_pages((gfp_mask), 0)