Re: [PATCH] block: Fix start and length check added to iov_iter_extract_bvecs()

[Keith Busch <kbusch@kernel.org>]

On Wed, Aug 26, 2026 at 07:18:37PM +0100, David Howells wrote:
> @@ -1921,15 +1921,19 @@ ssize_t iov_iter_extract_bvecs(struct iov_iter *iter, struct bio_vec *bv,
>  		unsigned short max_vecs, unsigned mem_align_mask,
>  		iov_iter_extraction_t extraction_flags)
>  {
> -	unsigned long start = (unsigned long)iter_iov_addr(iter);
>  	unsigned short entries_left = max_vecs - *nr_vecs;
>  	unsigned short nr_pages, i = 0;
>  	size_t left, offset, len;
>  	struct page **pages;
>  	ssize_t size;
>  
> -	if ((start | iter_iov_len(iter)) & mem_align_mask)
> +	if (iov_iter_alignment(iter) & mem_align_mask) {
> +		pr_warn("%u %zx %x\n",
> +			iter->iter_type,
> +			iov_iter_alignment(iter),
> +			mem_align_mask);
>  		return -EINVAL;
> +	}

iov_iter_alignment loops over all the vectors when we only need to
examine the current one here.