block: fix folio leak in bio_iov_iter_bounce_read()

If iov_iter_extract_bvecs() returns an error or zero bytes extracted,
then the folio allocated is leaked on return. Ensure it's put before
returning.

Fixes: 8dd5e7c ("block: add helpers to bounce buffer an iov_iter into bios")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

block/bio.c

@@ -1382,8 +1382,10 @@ static int bio_iov_iter_bounce_read(struct bio *bio, struct iov_iter *iter)
 		ret = iov_iter_extract_bvecs(iter, bio->bi_io_vec + 1, len,
 				&bio->bi_vcnt, bio->bi_max_vecs - 1, 0);
 		if (ret <= 0) {
-			if (!bio->bi_vcnt)
+			if (!bio->bi_vcnt) {
+				folio_put(folio);
 				return ret;
+			}
 			break;
 		}
 		len -= ret;