Re: [PATCH 24/44] iov_iter_get_pages_alloc(): lift freeing pages array on failure exits into wrapper

[Jeff Layton <jlayton@kernel.org>]

On Wed, 2022-06-22 at 05:15 +0100, Al Viro wrote:
> Incidentally, ITER_XARRAY did *not* free the sucker in case when
> iter_xarray_populate_pages() returned 0...
> 
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---
>  lib/iov_iter.c | 38 ++++++++++++++++++++++----------------
>  1 file changed, 22 insertions(+), 16 deletions(-)
> 
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index c3fb7853dbe8..9c25661684c6 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -1425,15 +1425,10 @@ static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
>  		maxsize = n;
>  	else
>  		npages = DIV_ROUND_UP(maxsize + off, PAGE_SIZE);
> -	p = get_pages_array(npages);
> +	*pages = p = get_pages_array(npages);
>  	if (!p)
>  		return -ENOMEM;
> -	n = __pipe_get_pages(i, maxsize, p, off);
> -	if (n > 0)
> -		*pages = p;
> -	else
> -		kvfree(p);
> -	return n;
> +	return __pipe_get_pages(i, maxsize, p, off);
>  }
>  
>  static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i,
> @@ -1463,10 +1458,9 @@ static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i,
>  			count++;
>  	}
>  
> -	p = get_pages_array(count);
> +	*pages = p = get_pages_array(count);
>  	if (!p)
>  		return -ENOMEM;
> -	*pages = p;
>  
>  	nr = iter_xarray_populate_pages(p, i->xarray, index, count);
>  	if (nr == 0)
> @@ -1475,7 +1469,7 @@ static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i,
>  	return min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
>  }
>  
> -ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
> +static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
>  		   struct page ***pages, size_t maxsize,
>  		   size_t *start)
>  {
> @@ -1501,16 +1495,12 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
>  
>  		addr = first_iovec_segment(i, &len, start, maxsize, ~0U);
>  		n = DIV_ROUND_UP(len, PAGE_SIZE);
> -		p = get_pages_array(n);
> +		*pages = p = get_pages_array(n);
>  		if (!p)
>  			return -ENOMEM;
>  		res = get_user_pages_fast(addr, n, gup_flags, p);
> -		if (unlikely(res <= 0)) {
> -			kvfree(p);
> -			*pages = NULL;
> +		if (unlikely(res <= 0))
>  			return res;
> -		}
> -		*pages = p;
>  		return (res == n ? len : res * PAGE_SIZE) - *start;
>  	}
>  	if (iov_iter_is_bvec(i)) {
> @@ -1531,6 +1521,22 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
>  		return iter_xarray_get_pages_alloc(i, pages, maxsize, start);
>  	return -EFAULT;
>  }
> +
> +ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
> +		   struct page ***pages, size_t maxsize,
> +		   size_t *start)
> +{
> +	ssize_t len;
> +
> +	*pages = NULL;
> +
> +	len = __iov_iter_get_pages_alloc(i, pages, maxsize, start);
> +	if (len <= 0) {
> +		kvfree(*pages);
> +		*pages = NULL;
> +	}
> +	return len;
> +}
>  EXPORT_SYMBOL(iov_iter_get_pages_alloc);
>  
>  size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,


Reviewed-by: Jeff Layton <jlayton@kernel.org>