Patch "nand: fix wrong default oob layout for small pages using soft ecc" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

nand: fix wrong default oob layout for small pages using soft ecc

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
nand-fix-wrong-default-oob-layout-for-small-pages-using-soft-ecc.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Miquel Raynal <[email protected]>
Date: Wed, 5 Jul 2017 08:51:09 +0200
Subject: nand: fix wrong default oob layout for small pages using soft ecc

From: Miquel Raynal <[email protected]>

commit f7f8c1756e9a5f1258a7cc6b663f8451b724900f upstream.

When using soft ecc, if no ooblayout is given, the core automatically uses one of the nand_ooblayout_{sp,lp}*() functions to determine the layout inside the out of band data.

Until kernel version 4.6, struct nand_ecclayout was used for that purpose. During the migration from 4.6 to 4.7, an error shown up in the small page layout, in the case oob section is only 8 bytes long.

The layout was using three bytes (0, 1, 2) for ecc, two bytes (3, 4) as free bytes, one byte (5) for bad block marker and finally two bytes (6, 7) as free bytes, as shown there:

[linux-4.6] drivers/mtd/nand/nand_base.c:52

static struct nand_ecclayout nand_oob_8 = {
	.eccbytes = 3,
	.eccpos = {0, 1, 2},
	.oobfree = {
		{.offset = 3,
		 .length = 2},
		{.offset = 6,
		 .length = 2} }
};

This fixes the current implementation which is incoherent. It references bit 3 at the same time as an ecc byte and a free byte.

Furthermore, it is clear with the previous implementation that there is only one ecc section with 8 bytes oob sections. We shall return -ERANGE in the nand_ooblayout_ecc_sp() function when asked for the second section.

---
 drivers/mtd/nand/nand_base.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

@@ -64,8 +64,14 @@ static int nand_ooblayout_ecc_sp(struct
 
 	if (!section) {
 		oobregion->offset = 0;
-		oobregion->length = 4;
+		if (mtd->oobsize == 16)
+			oobregion->length = 4;
+		else
+			oobregion->length = 3;
 	} else {
+		if (mtd->oobsize == 8)
+			return -ERANGE;
+
 		oobregion->offset = 6;
 		oobregion->length = ecc->total - 4;
 	}

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/nand-fix-wrong-default-oob-layout-for-small-pages-using-soft-ecc.patch