mtd: nand: cleanup the nand_do_write_ops

nand_do_write_ops was broken in regard to writing several pages, each 
with its own oob.

Although nand_do_write_ops intends to allow such mode, it fails do do so
Probably this was never tested.

Also add missing checks for attempts to write at illegal offsets.
Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/nand/nand_base.c

@@ -2072,11 +2072,9 @@ static int nand_write_page(struct mtd_info *mtd, struct nand_chip *chip,
  * @oob:	oob data buffer
  * @ops:	oob ops structure
  */
-static uint8_t *nand_fill_oob(struct nand_chip *chip, uint8_t *oob,
+static uint8_t *nand_fill_oob(struct nand_chip *chip, uint8_t *oob, size_t len,
 						struct mtd_oob_ops *ops)
 {
-	size_t len = ops->ooblen;
-
 	switch(ops->mode) {
 
 	case MTD_OOB_PLACE:
@@ -2131,6 +2129,11 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
 	int chipnr, realpage, page, blockmask, column;
 	struct nand_chip *chip = mtd->priv;
 	uint32_t writelen = ops->len;
+
+	uint32_t oobwritelen = ops->ooblen;
+	uint32_t oobmaxlen = ops->mode == MTD_OOB_AUTO ?
+				mtd->oobavail : mtd->oobsize;
+
 	uint8_t *oob = ops->oobbuf;
 	uint8_t *buf = ops->datbuf;
 	int ret, subpage;
@@ -2172,6 +2175,10 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
 	if (likely(!oob))
 		memset(chip->oob_poi, 0xff, mtd->oobsize);
 
+	/* Don't allow multipage oob writes with offset */
+	if (ops->ooboffs && (ops->ooboffs + ops->ooblen > oobmaxlen))
+		return -EINVAL;
+
 	while(1) {
 		int bytes = mtd->writesize;
 		int cached = writelen > bytes && page != blockmask;
@@ -2187,8 +2194,11 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
 			wbuf = chip->buffers->databuf;
 		}
 
-		if (unlikely(oob))
-			oob = nand_fill_oob(chip, oob, ops);
+		if (unlikely(oob)) {
+			size_t len = min(oobwritelen, oobmaxlen);
+			oob = nand_fill_oob(chip, oob, len, ops);
+			oobwritelen -= len;
+		}
 
 		ret = chip->write_page(mtd, chip, wbuf, page, cached,
 				       (ops->mode == MTD_OOB_RAW));
@@ -2362,7 +2372,7 @@ static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
 		chip->pagebuf = -1;
 
 	memset(chip->oob_poi, 0xff, mtd->oobsize);
-	nand_fill_oob(chip, ops->oobbuf, ops);
+	nand_fill_oob(chip, ops->oobbuf, ops->ooblen, ops);
 	status = chip->ecc.write_oob(mtd, chip, page & chip->pagemask);
 	memset(chip->oob_poi, 0xff, mtd->oobsize);