linux-kernel - Re: [PATCH] dm: writecache: Use 2-factor allocator arguments

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Date:   Mon, 18 Jun 2018 17:12:53 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@...hat.com>
To:     Kees Cook <keescook@...omium.org>
cc:     linux-kernel@...r.kernel.org, dm-devel@...hat.com,
        Dan Williams <dan.j.williams@...el.com>,
        Mike Snitzer <msnitzer@...hat.com>,
        Alasdair Kergon <agk@...hat.com>
Subject: Re: [PATCH] dm: writecache: Use 2-factor allocator arguments



On Mon, 18 Jun 2018, Kees Cook wrote:

> This adjusts the allocator calls to use the 2-factor argument style, as
> already done treewide for better defense against allocator overflows.
> Additionally adjusts style nit to avoid assignments in test expressions.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  drivers/md/dm-writecache.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
> index 5961c7794ef3..7773f4c75701 100644
> --- a/drivers/md/dm-writecache.c
> +++ b/drivers/md/dm-writecache.c
> @@ -259,7 +259,7 @@ static int persistent_memory_claim(struct dm_writecache *wc)
>  	if (da != p) {
>  		long i;
>  		wc->memory_map = NULL;
> -		pages = kvmalloc(p * sizeof(struct page *), GFP_KERNEL);
> +		pages = kvmalloc_array(p, sizeof(struct page *), GFP_KERNEL);
>  		if (!pages) {
>  			r = -ENOMEM;
>  			goto err2;
> @@ -859,7 +859,8 @@ static int writecache_alloc_entries(struct dm_writecache *wc)
>  
>  	if (wc->entries)
>  		return 0;
> -	wc->entries = vmalloc(sizeof(struct wc_entry) * wc->n_blocks);
> +	wc->entries = vmalloc(array_size(sizeof(struct wc_entry),
> +					 wc->n_blocks));
>  	if (!wc->entries)
>  		return -ENOMEM;
>  	for (b = 0; b < wc->n_blocks; b++) {
> @@ -1480,10 +1481,13 @@ static void __writecache_writeback_pmem(struct dm_writecache *wc, struct writeba
>  		bio_set_dev(&wb->bio, wc->dev->bdev);
>  		wb->bio.bi_iter.bi_sector = read_original_sector(wc, e);
>  		wb->page_offset = PAGE_SIZE;
> -		if (max_pages <= WB_LIST_INLINE ||
> -		    unlikely(!(wb->wc_list = kmalloc(max_pages * sizeof(struct wc_entry *),
> -						     GFP_NOIO | __GFP_NORETRY |
> -						     __GFP_NOMEMALLOC | __GFP_NOWARN)))) {
> +		if (max_pages > WB_LIST_INLINE)
> +			wb->wc_list = kmalloc_array(max_pages,
> +						    sizeof(struct wc_entry *),
> +						    GFP_NOIO | __GFP_NORETRY |
> +						    __GFP_NOMEMALLOC |
> +						    __GFP_NOWARN);
> +		if (max_pages <= WB_LIST_INLINE || !wb->wc_list) {

The rest of patch is OK - but you shouldn't duplicate the comparison 
against WB_LIST_INLINE.

Mikulas

>  			wb->wc_list = wb->wc_list_inline;
>  			max_pages = WB_LIST_INLINE;
>  		}
> -- 
> 2.17.0
> 
> 
> -- 
> Kees Cook
> Pixel Security
>