On Thu, Oct 17, 2024 at 12:42 AM Feng Tang <feng.tang@xxxxxxxxx> wrote:
>
> When 'orig_size' of kmalloc object is enabled by debug option, it
> should either contains the actual requested size or the cache's
> 'object_size'.
>
> But it's not true if that object is a kfence-allocated one, and the
> data at 'orig_size' offset of metadata could be zero or other values.
> This is not a big issue for current 'orig_size' usage, as init_object()
> and check_object() during alloc/free process will be skipped for kfence
> addresses. But it could cause trouble for other usage in future.
>
> Use the existing kfence helper kfence_ksize() which can return the
> real original request size.
>
> Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
> ---
Looks good to me,
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
> mm/slub.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index af9a80071fe0..1d348899f7a3 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -768,6 +768,9 @@ static inline unsigned int get_orig_size(struct kmem_cache *s, void *object)
> {
> void *p = kasan_reset_tag(object);
>
> + if (is_kfence_address(object))
> + return kfence_ksize(object);
> +
> if (!slub_debug_orig_size(s))
> return s->object_size;
>
> --
> 2.27.0
>
