ACK/cmnt: [SRU][Xenial][PATCH 1/1] more bio_map_user_iov() leak fixes

[Stefan Bader]

On 08.12.2017 13:38, Kleber Sacilotto de Souza wrote:
> From: Al Viro <viro at zeniv.linux.org.uk>
> 
> we need to take care of failure exit as well - pages already
> in bio should be dropped by analogue of bio_unmap_pages(),
> since their refcounts had been bumped only once per reference
> in bio.
> 
> Cc: stable at vger.kernel.org
> Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
> 
> CVE-CVE-2017-12190
> (backported from commit 2b04e8f6bbb196cab4b232af0f8d48ff2c7a8058)
> [klebers: page_cache_release() is defined as put_page(), but keep it as
>  page_cache_release() for consistency with the rest of the code.]
> Signed-off-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>

> ---

Same provisional ack in case both functions are the same.

>  block/bio.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/block/bio.c b/block/bio.c
> index 68bbc835bacc..6750552d6b16 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -1268,6 +1268,7 @@ struct bio *bio_map_user_iov(struct request_queue *q,
>  	int ret, offset;
>  	struct iov_iter i;
>  	struct iovec iov;
> +	struct bio_vec *bvec;
>  
>  	iov_for_each(iov, i, *iter) {
>  		unsigned long uaddr = (unsigned long) iov.iov_base;
> @@ -1312,7 +1313,12 @@ struct bio *bio_map_user_iov(struct request_queue *q,
>  		ret = get_user_pages_fast(uaddr, local_nr_pages,
>  				(iter->type & WRITE) != WRITE,
>  				&pages[cur_page]);
> -		if (ret < local_nr_pages) {
> +		if (unlikely(ret < local_nr_pages)) {
> +			for (j = cur_page; j < page_limit; j++) {
> +				if (!pages[j])
> +					break;
> +				put_page(pages[j]);
> +			}
>  			ret = -EFAULT;
>  			goto out_unmap;
>  		}
> @@ -1374,10 +1380,8 @@ struct bio *bio_map_user_iov(struct request_queue *q,
>  	return bio;
>  
>   out_unmap:
> -	for (j = 0; j < nr_pages; j++) {
> -		if (!pages[j])
> -			break;
> -		page_cache_release(pages[j]);
> +	bio_for_each_segment_all(bvec, bio, j) {
> +		page_cache_release(bvec->bv_page);
>  	}
>   out:
>  	kfree(pages);
> 


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