On Tue, Aug 17, 2021 at 10:31:32PM -0700, Joe Perches wrote:

On Tue, 2021-08-17 at 22:08 -0700, Kees Cook wrote:

quoted

As already done in GrapheneOS, add the __alloc_size attribute for
regular kmalloc interfaces, to provide additional hinting for better
bounds checking, assisting CONFIG_FORTIFY_SOURCE and other compiler
optimizations.

[]

quoted

diff --git a/include/linux/slab.h b/include/linux/slab.h

[]

quoted

@@ -181,7 +181,7 @@ int kmem_cache_shrink(struct kmem_cache *);

 /*
  * Common kmalloc functions provided by all allocators
  */
-void * __must_check krealloc(const void *, size_t, gfp_t);
+void * __must_check krealloc(const void *, size_t, gfp_t) __alloc_size(2);

I suggest the __alloc_size attribute be placed at the beginning of the
function declaration to be more similar to the common __printf attribute
location uses.

Yeah, any consistent ordering suggestions are welcome here; thank you!
These declarations were all over the place, and trying to follow each
slightly different existing style made my eyes hurt. :)

__alloc_size(2)
void * __must_check krealloc(const void *, size_t, gfp_t);

I really prefer the __must_check to be with the other attribute and that
function declarations have argument names too like:

__alloc_size(2) __must_check
void *krealloc(const void *ptr, size_t size, gfp_t gfp);

I'm happy with whatever makes the most sense.

but there are a _lot_ of placement of __must_check after the return type

Lastly __alloc_size should probably be added to checkpatch

Oh, yes! Thanks for the reminder.

Why the "{0,5}" bit here? I was expecting just "?". (i.e. it can have
either 1 or 2 arguments.)

 		  }x;
 our $Modifier;
 our $Inline	= qr{inline|__always_inline|noinline|__inline|__inline__};

-- 
Kees Cook