[RFC] bio: fix page leak bio_add_hw_page failure

[Pavel Begunkov <asml.silence@gmail.com>]

__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@vger.kernel.org # 5.8+
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---

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;
+			}
 			__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);
 			ret = -EINVAL;
 			break;
 		}
-- 
2.32.0