UBI: fix out of bounds write

If aeb->len >= vol->reserved_pebs, we should not be writing aeb into the
PEB->LEB mapping.

Caught by Coverity, CID #711212.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index 16e34b3..8c9a710 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -1419,7 +1419,8 @@
 				 * during re-size.
 				 */
 				ubi_move_aeb_to_list(av, aeb, &ai->erase);
-			vol->eba_tbl[aeb->lnum] = aeb->pnum;
+			else
+				vol->eba_tbl[aeb->lnum] = aeb->pnum;
 		}
 	}