Re: [PATCH v3] mempool: Do not use ksize() for poisoning

[Andrey Konovalov <andreyknvl@gmail.com>]

On Wed, Oct 26, 2022 at 1:36 AM Kees Cook <keescook@chromium.org> wrote:
>
> Nothing appears to be using ksize() within the kmalloc-backed mempools
> except the mempool poisoning logic. Use the actual pool size instead
> of the ksize() to avoid needing any special handling of the memory as
> needed by KASAN, UBSAN_BOUNDS, nor FORTIFY_SOURCE.
>
> Suggested-by: Vlastimil Babka <vbabka@suse.cz>
> Link: https://lore.kernel.org/lkml/f4fc52c4-7c18-1d76-0c7a-4058ea2486b9@suse.cz/
> Cc: Andrey Konovalov <andreyknvl@gmail.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Marco Elver <elver@google.com>
> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: linux-mm@kvack.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> v3: remove ksize() calls instead of adding kmalloc_roundup_size() calls (vbabka)
> v2: https://lore.kernel.org/lkml/20221018090323.never.897-kees@kernel.org/
> v1: https://lore.kernel.org/lkml/20220923202822.2667581-14-keescook@chromium.org/
> ---
>  mm/mempool.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/mempool.c b/mm/mempool.c
> index 96488b13a1ef..54204065037d 100644
> --- a/mm/mempool.c
> +++ b/mm/mempool.c
> @@ -58,7 +58,7 @@ static void check_element(mempool_t *pool, void *element)
>  {
>         /* Mempools backed by slab allocator */
>         if (pool->free == mempool_free_slab || pool->free == mempool_kfree) {
> -               __check_element(pool, element, ksize(element));
> +               __check_element(pool, element, (size_t)pool->pool_data);
>         } else if (pool->free == mempool_free_pages) {
>                 /* Mempools backed by page allocator */
>                 int order = (int)(long)pool->pool_data;
> @@ -81,7 +81,7 @@ static void poison_element(mempool_t *pool, void *element)
>  {
>         /* Mempools backed by slab allocator */
>         if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc) {
> -               __poison_element(element, ksize(element));
> +               __poison_element(element, (size_t)pool->pool_data);
>         } else if (pool->alloc == mempool_alloc_pages) {
>                 /* Mempools backed by page allocator */
>                 int order = (int)(long)pool->pool_data;
> @@ -112,7 +112,7 @@ static __always_inline void kasan_poison_element(mempool_t *pool, void *element)
>  static void kasan_unpoison_element(mempool_t *pool, void *element)
>  {
>         if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
> -               kasan_unpoison_range(element, __ksize(element));
> +               kasan_unpoison_range(element, (size_t)pool->pool_data);
>         else if (pool->alloc == mempool_alloc_pages)
>                 kasan_unpoison_pages(element, (unsigned long)pool->pool_data,
>                                      false);
> --
> 2.34.1
>

For the KASAN change:

Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>

Thanks!