Subject: Re: [PATCH 1/2] mm, treewide: Rename kzfree() to kfree_sensitive()

From: Dan Carpenter <[email-masked]>
Date: Mon, 15 Jun 2020 21:07:53 +0300

On Mon, Apr 13, 2020 at 05:15:49PM -0400, Waiman Long wrote:
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 23c7500eea7d..c08bc7eb20bd 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -1707,17 +1707,17 @@ void *krealloc(const void *p, size_t new_size, gfp_t flags)
>  EXPORT_SYMBOL(krealloc);
>  
>  /**
> - * kzfree - like kfree but zero memory
> + * kfree_sensitive - Clear sensitive information in memory before freeing
>   * @p: object to free memory of
>   *
>   * The memory of the object @p points to is zeroed before freed.
> - * If @p is %NULL, kzfree() does nothing.
> + * If @p is %NULL, kfree_sensitive() does nothing.
>   *
>   * Note: this function zeroes the whole allocated buffer which can be a good
>   * deal bigger than the requested buffer size passed to kmalloc(). So be
>   * careful when using this function in performance sensitive code.
>   */
> -void kzfree(const void *p)
> +void kfree_sensitive(const void *p)
>  {
>  	size_t ks;
>  	void *mem = (void *)p;
> @@ -1725,10 +1725,10 @@ void kzfree(const void *p)
>  	if (unlikely(ZERO_OR_NULL_PTR(mem)))
>  		return;
>  	ks = ksize(mem);
> -	memset(mem, 0, ks);
> +	memzero_explicit(mem, ks);
        ^^^^^^^^^^^^^^^^^^^^^^^^^
This is an unrelated bug fix.  It really needs to be pulled into a
separate patch by itself and back ported to stable kernels.

>  	kfree(mem);
>  }
> -EXPORT_SYMBOL(kzfree);
> +EXPORT_SYMBOL(kfree_sensitive);
>  
>  /**
>   * ksize - get the actual amount of memory allocated for a given object

regards,
dan carpenter