linux-kernel - [PATCH 4.4 54/67] nvmem: mxs-ocotp: fix buffer overflow in read

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Date:	Mon,  9 May 2016 09:18:59 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Stefan Wahren <stefan.wahren@...e.com>,
	Stanislav Meduna <stano@...una.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: [PATCH 4.4 54/67] nvmem: mxs-ocotp: fix buffer overflow in read

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

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

From: Stanislav Meduna <stano@...una.org>

commit d1306eb675ad7a9a760b6b8e8e189824b8db89e7 upstream.

This patch fixes the issue where the mxs_ocotp_read is reading
the ocotp in reg_size steps but decrements the remaining size
by 1. The number of iterations is thus four times higher,
overwriting the area behind the output buffer.

Fixes: c01e9a11ab6f ("nvmem: add driver for ocotp in i.MX23 and i.MX28")
Tested-by: Stefan Wahren <stefan.wahren@...e.com>
Signed-off-by: Stanislav Meduna <stano@...una.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/nvmem/mxs-ocotp.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/nvmem/mxs-ocotp.c
+++ b/drivers/nvmem/mxs-ocotp.c
@@ -94,7 +94,7 @@ static int mxs_ocotp_read(void *context,
 	if (ret)
 		goto close_banks;
 
-	while (val_size) {
+	while (val_size >= reg_size) {
 		if ((offset < OCOTP_DATA_OFFSET) || (offset % 16)) {
 			/* fill up non-data register */
 			*buf = 0;
@@ -103,7 +103,7 @@ static int mxs_ocotp_read(void *context,
 		}
 
 		buf++;
-		val_size--;
+		val_size -= reg_size;
 		offset += reg_size;
 	}