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

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Date:   Wed, 26 Oct 2022 12:02:53 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andrey Konovalov <andreyknvl@...il.com>,
        David Rientjes <rientjes@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v3] mempool: Do not use ksize() for poisoning

On 10/26/22 01:36, Kees Cook 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@...e.cz>
> Link: https://lore.kernel.org/lkml/f4fc52c4-7c18-1d76-0c7a-4058ea2486b9@suse.cz/
> Cc: Andrey Konovalov <andreyknvl@...il.com>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Marco Elver <elver@...gle.com>
> Cc: Vincenzo Frascino <vincenzo.frascino@....com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: linux-mm@...ck.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
> 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);