CIFS: Fix possible buffer corruption in cifs_user_read()

If there was a short read in the middle of the rdata list,
we can end up with a corrupt output buffer.

Signed-off-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 3ea6fc86a471..c3390e2c6e0d 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -3049,7 +3049,9 @@ again:
                         } else {
                                 rc = cifs_readdata_to_iov(rdata, to);
                         }
-
+                        /* if there was a short read -- discard anything left */
+                        if (rdata->got_bytes && rdata->got_bytes < rdata->bytes)
+                                rc = -ENODATA;
                 }
                 list_del_init(&rdata->list);
                 kref_put(&rdata->refcount, cifs_uncached_readdata_release);