@@ -146,6 +146,28 @@ int ubi_io_read(const struct ubi_device *ubi, void *buf, int pnum, int offset,
+ * Deliberately corrupt the buffer to improve robustness. Indeed, if we
+ * do not do this, the following may happen:
+ * 1. The buffer contains data from previous operation, e.g., read from
+ * another PEB previously. The data looks like expected, e.g., if we
+ * just do not read anything and return - the caller would not
+ * notice this. E.g., if we are reading a VID header, the buffer may
+ * contain a valid VID header from another PEB.
+ * 2. The driver is buggy and returns us success or -EBADMSG or
+ * -EUCLEAN, but it does not actually put any data to the buffer.
+ * This may confuse UBI or upper layers - they may think the buffer
+ * contains valid data while in fact it is just old data. This is
+ * especially possible because UBI (and UBIFS) relies on CRC, and
+ * treats data as correct even in case of ECC errors if the CRC is
+ * correct.
+ * Try to prevent this situation by changing the first byte of the
+ * buffer.
+ *((uint8_t *)buf) ^= 0xFF;
addr = (loff_t)pnum * ubi->peb_size + offset;
err = ubi->mtd->read(ubi->mtd, addr, len, &read, buf);