block: check for proper length of iov entries earlier in blk_rq_map_user_iov()

commit 9284bcf checks for proper length of iov entries in
blk_rq_map_user_iov(). But if the map is unaligned, kernel
will break out the loop without checking for the proper length.
So we need to check the proper length before the unalign check.

Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/block/blk-map.c b/block/blk-map.c
index 5d5dbe47c228..e663ac2d8e68 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -201,12 +201,13 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
         for (i = 0; i < iov_count; i++) {
                 unsigned long uaddr = (unsigned long)iov[i].iov_base;
 
+                if (!iov[i].iov_len)
+                        return -EINVAL;
+
                 if (uaddr & queue_dma_alignment(q)) {
                         unaligned = 1;
                         break;
                 }
-                if (!iov[i].iov_len)
-                        return -EINVAL;
         }
 
         if (unaligned || (q->dma_pad_mask & len) || map_data)