bio: fix memcpy corruption in bio_copy_user_iov()

st driver uses blk_rq_map_user() in order to just build a request out
of page frames. In this case, map_data->offset is a non zero value and
iov[0].iov_base is NULL. We need to increase nr_pages for that.

Cc: stable@kernel.org
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/bio.c b/fs/bio.c
index 7bbc98f0eda1..98711647ece4 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -817,6 +817,9 @@ struct bio *bio_copy_user_iov(struct request_queue *q,
                 len += iov[i].iov_len;
         }
 
+        if (offset)
+                nr_pages++;
+
         bmd = bio_alloc_map_data(nr_pages, iov_count, gfp_mask);
         if (!bmd)
                 return ERR_PTR(-ENOMEM);