linux-kernel - [PATCH 3.13 043/198] mtd: nand: omap: fix BCHx ecc.correct to return detected bit-flips in erased-page

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Message-Id: <1405459868-15089-44-git-send-email-kamal@canonical.com>
Date:	Tue, 15 Jul 2014 14:28:33 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Pekon Gupta <pekon@...com>,
	Brian Norris <computersforpeace@...il.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13 043/198] mtd: nand: omap: fix BCHx ecc.correct to return detected bit-flips in erased-page

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

------------------

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

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: Kamal Mostafa <kamal@...onical.com>
---
 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 2365b5a..b594e61 100644
--- a/drivers/mtd/nand/omap2.c
+++ b/drivers/mtd/nand/omap2.c
@@ -1451,7 +1451,7 @@ 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);
-- 
1.9.1

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