On Mon, Jul 19, 2021 at 11:53:00AM +0100, Pavel Begunkov wrote:
> __bio_iov_append_get_pages() doesn't put not appended pages on
> bio_add_hw_page() failure, so potentially leaking them, fix it. Also, do
> the same for __bio_iov_iter_get_pages(), even though it looks like it
> can't be triggered by userspace in this case.
>
> Fixes: 0512a75b98f8 ("block: Introduce REQ_OP_ZONE_APPEND")
> Cc: stable@xxxxxxxxxxxxxxx # 5.8+
> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> ---
>
> I haven't tested the fail path, thus RFC. Would be great if someone can
> do it or take over the fix.
>
> block/bio.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 1fab762e079b..d95e3456ba0c 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -979,6 +979,14 @@ static int bio_iov_bvec_set_append(struct bio *bio, struct iov_iter *iter)
> return 0;
> }
>
> +static void bio_put_pages(struct page **pages, size_t size, size_t off)
> +{
> + size_t i, nr = DIV_ROUND_UP(size + (off & ~PAGE_MASK), PAGE_SIZE);
> +
> + for (i = 0; i < nr; i++)
> + put_page(pages[i]);
> +}
> +
> #define PAGE_PTRS_PER_BVEC (sizeof(struct bio_vec) / sizeof(struct page *))
>
> /**
> @@ -1023,8 +1031,10 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
> if (same_page)
> put_page(page);
> } else {
> - if (WARN_ON_ONCE(bio_full(bio, len)))
> - return -EINVAL;
> + if (WARN_ON_ONCE(bio_full(bio, len))) {
> + bio_put_pages(pages + i, left, offset);
> + return -EINVAL;
> + }
It is unlikely to happen:
unsigned short nr_pages = bio->bi_max_vecs - bio->bi_vcnt;
struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt;
struct page **pages = (struct page **)bv;
pages += entries_left * (PAGE_PTRS_PER_BVEC - 1);
size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
> __bio_add_page(bio, page, len, offset);
> }
> offset = 0;
> @@ -1069,6 +1079,7 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter)
> len = min_t(size_t, PAGE_SIZE - offset, left);
> if (bio_add_hw_page(q, bio, page, len, offset,
> max_append_sectors, &same_page) != len) {
> + bio_put_pages(pages + i, left, offset);
Same with above.
Thanks,
Ming
