[PATCH v2 2/4] mtdchar: bound OOB reads to the data in intermediate chunks

[James Hilliard <james.hilliard1@gmail.com>]

MEMREAD limits the data and OOB lengths independently for each call to
mtd_read_oob(). A backend such as SPI-NAND continues reading until both
streams are exhausted, so an intermediate call can read OOB from pages
beyond the end of its data chunk.

The next call advances by the data bytes transferred, not by the pages
visited for OOB. If OOB remains, it starts again at pages already read
and returns their OOB a second time.

Limit OOB in intermediate reads to the pages covered by their data,
as MEMWRITE already does. Leave the final call unchanged so SPI-NAND
can still return additional OOB pages when no data chunk follows.

Fixes: 095bb6e44eb1 ("mtdchar: add MEMREAD ioctl")
Cc: stable@vger.kernel.org
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
---
 drivers/mtd/mtdchar.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index 19d33dacb62d..189e462a9df0 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -769,6 +769,9 @@ mtdchar_read_ioctl(struct mtd_info *mtd, struct mtd_read_req __user *argp)
 		if (ops.len == mtd->erasesize)
 			ops.len -= mtd_mod_by_ws(req.start + ops.len, mtd);
 
+		if (ops.len < req.len)
+			adjust_oob_length(mtd, req.start, &ops);
+
 		ret = mtd_read_oob(mtd, (loff_t)req.start, &ops);
 
 		req.ecc_stats.uncorrectable_errors +=

-- 
2.53.0