linux-kernel - [PATCH 2/2] nvmem: imx-ocotp: fix MAC address byte length

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Message-ID: <20250712181729.6495-3-srini@kernel.org>
Date: Sat, 12 Jul 2025 19:17:27 +0100
From: srini@...nel.org
To: gregkh@...uxfoundation.org
Cc: linux-kernel@...r.kernel.org,
	Steffen Bätz <steffen@...osonix.de>,
	stable@...r.kernel.org,
	Alexander Stein <alexander.stein@...tq-group.com>,
	Srinivas Kandagatla <srini@...nel.org>
Subject: [PATCH 2/2] nvmem: imx-ocotp: fix MAC address byte length

From: Steffen Bätz <steffen@...osonix.de>

The commit "13bcd440f2ff nvmem: core: verify cell's raw_len" caused an
extension of the "mac-address" cell from 6 to 8 bytes due to word_size
of 4 bytes. This led to a required byte swap of the full buffer length,
which caused truncation of the mac-address when read.

Previously, the mac-address was incorrectly truncated from
70:B3:D5:14:E9:0E to 00:00:70:B3:D5:14.

Fix the issue by swapping only the first 6 bytes to correctly pass the
mac-address to the upper layers.

Fixes: 13bcd440f2ff ("nvmem: core: verify cell's raw_len")
Cc: stable@...r.kernel.org
Signed-off-by: Steffen Bätz <steffen@...osonix.de>
Tested-by: Alexander Stein <alexander.stein@...tq-group.com>
Signed-off-by: Srinivas Kandagatla <srini@...nel.org>
---
 drivers/nvmem/imx-ocotp-ele.c | 5 ++++-
 drivers/nvmem/imx-ocotp.c     | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/nvmem/imx-ocotp-ele.c b/drivers/nvmem/imx-ocotp-ele.c
index ca6dd71d8a2e..7807ec0e2d18 100644
--- a/drivers/nvmem/imx-ocotp-ele.c
+++ b/drivers/nvmem/imx-ocotp-ele.c
@@ -12,6 +12,7 @@
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
+#include <linux/if_ether.h>	/* ETH_ALEN */
 
 enum fuse_type {
 	FUSE_FSB = BIT(0),
@@ -118,9 +119,11 @@ static int imx_ocotp_cell_pp(void *context, const char *id, int index,
 	int i;
 
 	/* Deal with some post processing of nvmem cell data */
-	if (id && !strcmp(id, "mac-address"))
+	if (id && !strcmp(id, "mac-address")) {
+		bytes = min(bytes, ETH_ALEN);
 		for (i = 0; i < bytes / 2; i++)
 			swap(buf[i], buf[bytes - i - 1]);
+	}
 
 	return 0;
 }
diff --git a/drivers/nvmem/imx-ocotp.c b/drivers/nvmem/imx-ocotp.c
index 79dd4fda0329..7bf7656d4f96 100644
--- a/drivers/nvmem/imx-ocotp.c
+++ b/drivers/nvmem/imx-ocotp.c
@@ -23,6 +23,7 @@
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/delay.h>
+#include <linux/if_ether.h>	/* ETH_ALEN */
 
 #define IMX_OCOTP_OFFSET_B0W0		0x400 /* Offset from base address of the
 					       * OTP Bank0 Word0
@@ -227,9 +228,11 @@ static int imx_ocotp_cell_pp(void *context, const char *id, int index,
 	int i;
 
 	/* Deal with some post processing of nvmem cell data */
-	if (id && !strcmp(id, "mac-address"))
+	if (id && !strcmp(id, "mac-address")) {
+		bytes = min(bytes, ETH_ALEN);
 		for (i = 0; i < bytes / 2; i++)
 			swap(buf[i], buf[bytes - i - 1]);
+	}
 
 	return 0;
 }
-- 
2.43.0