UBI: do not let to read too much

In case of static volumes it is prohibited to read more data
then available.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
index d352c4575c3..14c66b48798 100644
--- a/drivers/mtd/ubi/kapi.c
+++ b/drivers/mtd/ubi/kapi.c
@@ -319,9 +319,14 @@ int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
             offset + len > vol->usable_leb_size)
                 return -EINVAL;
 
-        if (vol->vol_type == UBI_STATIC_VOLUME && lnum == vol->used_ebs - 1 &&
-            offset + len > vol->last_eb_bytes)
-                return -EINVAL;
+        if (vol->vol_type == UBI_STATIC_VOLUME) {
+                if (vol->used_ebs == 0)
+                        /* Empty static UBI volume */
+                        return 0;
+                if (lnum == vol->used_ebs - 1 &&
+                    offset + len > vol->last_eb_bytes)
+                        return -EINVAL;
+        }
 
         if (vol->upd_marker)
                 return -EBADF;