linux-hardening - Re: [PATCH] mempool: Use kmalloc_size

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Message-Id: <20221018155137.f6898d165aade2e3a5f0b2d3@linux-foundation.org>
Date:   Tue, 18 Oct 2022 15:51:37 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] mempool: Use kmalloc_size_roundup() to match ksize()
 usage

On Tue, 18 Oct 2022 02:03:29 -0700 Kees Cook <keescook@...omium.org> wrote:

> Round up allocations with kmalloc_size_roundup() so that mempool's use
> of ksize() is always accurate and no special handling of the memory is
> needed by KASAN, UBSAN_BOUNDS, nor FORTIFY_SOURCE.

Confused.  If the special handling is not needed, why doesn't the patch
removed the no longer needed special handling?

> 
> diff --git a/mm/mempool.c b/mm/mempool.c
> index 96488b13a1ef..0f3107b28e6b 100644
> --- a/mm/mempool.c
> +++ b/mm/mempool.c
> @@ -526,7 +526,7 @@ EXPORT_SYMBOL(mempool_free_slab);
>   */
>  void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
>  {
> -	size_t size = (size_t)pool_data;
> +	size_t size = kmalloc_size_roundup((size_t)pool_data);
>  	return kmalloc(size, gfp_mask);
>  }
>  EXPORT_SYMBOL(mempool_kmalloc);
> -- 
> 2.34.1