linux-kernel - [PATCH 3.12 077/170] mtd: nand: omap: fix BCHx ecc.correct to return detected bit-flips in erased-page

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Message-Id: <62874b837dc5de00f3c8de646e80b73c52d75b01.1405685481.git.jslaby@suse.cz>
Date:	Fri, 18 Jul 2014 14:11:22 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, pekon gupta <pekon@...com>,
	Brian Norris <computersforpeace@...il.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 077/170] mtd: nand: omap: fix BCHx ecc.correct to return detected bit-flips in erased-page

From: pekon gupta <pekon@...com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit f306e8c3b667632952f1a4a74ffb910bbc06255f upstream.

fixes: commit 62116e5171e00f85a8d53f76e45b84423c89ff34
       mtd: nand: omap2: Support for hardware BCH error correction.

In omap_elm_correct_data(), if bitflip_count in an erased-page is within the
correctable limit (< ecc.strength), then it is not indicated back to the caller
ecc->read_page().

This mis-guides upper layers like MTD and UBIFS layer to assume erased-page as
perfectly clean and use it for writing even if actual bitflip_count was
dangerously high (bitflip_count > mtd->bitflip_threshold).

This patch fixes this above issue, by returning 'stats' to caller
ecc->read_page() under all scenarios.

Reported-by: Brian Norris <computersforpeace@...il.com>
Signed-off-by: Pekon Gupta <pekon@...com>
Signed-off-by: Brian Norris <computersforpeace@...il.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/mtd/nand/omap2.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
index 4ecf0e5fd484..0332d0b2d73a 100644
--- a/drivers/mtd/nand/omap2.c
+++ b/drivers/mtd/nand/omap2.c
@@ -1463,7 +1463,7 @@ static int omap_elm_correct_data(struct mtd_info *mtd, u_char *data,
 
 	/* Check if any error reported */
 	if (!is_error_reported)
-		return 0;
+		return stat;
 
 	/* Decode BCH error using ELM module */
 	elm_decode_bch_error_page(info->elm_dev, ecc_vec, err_vec);
-- 
2.0.0

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