Index: head/stand/libsa/zfs/zfs.c
===================================================================
--- head/stand/libsa/zfs/zfs.c
+++ head/stand/libsa/zfs/zfs.c
@@ -435,8 +435,8 @@
 			ret = EIO;
 			goto error;
 		}
-		memcpy(outbuf, bouncebuf + head, secsz - head);
-		outbuf += secsz - head;
+		memcpy(outbuf, bouncebuf + head, min(secsz - head, bytes));
+		outbuf += min(secsz - head, bytes);
 	}
 
 	/* Full data return from read sectors */