linux-kernel - Re: [PATCH v2] nvmem: imx-ocotp: fix MAC address byte length

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Message-ID: <87ldpikdke.fsf@tarshish>
Date: Mon, 23 Jun 2025 12:33:05 +0300
From: Baruch Siach <baruch@...s.co.il>
To: Steffen Bätz <steffen@...osonix.de>
Cc: stable@...r.kernel.org,  Srinivas Kandagatla <srini@...nel.org>,  Shawn
 Guo <shawnguo@...nel.org>,  Sascha Hauer <s.hauer@...gutronix.de>,
  Pengutronix Kernel Team <kernel@...gutronix.de>,  Fabio Estevam
 <festevam@...il.com>,  Dmitry Baryshkov <lumag@...nel.org>,  Greg
 Kroah-Hartman <gregkh@...uxfoundation.org>,  imx@...ts.linux.dev,
  linux-arm-kernel@...ts.infradead.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] nvmem: imx-ocotp: fix MAC address byte length

Hi Steffen,

On Mon, Jun 23 2025, Steffen Bätz wrote:
> 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.
>
> Thus, the required byte swap for the mac-address of the full buffer length,
> caused an trucation of the read mac-address.
> From the original address 70:B3:D5:14:E9:0E to 00:00:70:B3:D5:14
>
> After swapping only the first 6 bytes, the mac-address is correctly passed
> 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>
> ---
> v2:
> - Add Cc: stable@...r.kernel.org as requested by Greg KH's patch bot
>  drivers/nvmem/imx-ocotp-ele.c | 2 ++
>  drivers/nvmem/imx-ocotp.c     | 2 ++
>  2 files changed, 4 insertions(+)
>
> diff --git a/drivers/nvmem/imx-ocotp-ele.c b/drivers/nvmem/imx-ocotp-ele.c
> index ca6dd71d8a2e..3af7968f5a34 100644
> --- a/drivers/nvmem/imx-ocotp-ele.c
> +++ b/drivers/nvmem/imx-ocotp-ele.c
> @@ -119,6 +119,8 @@ static int imx_ocotp_cell_pp(void *context, const char *id, int index,
>  
>  	/* Deal with some post processing of nvmem cell data */
>  	if (id && !strcmp(id, "mac-address"))
> +		if (bytes > 6)
> +			bytes = 6;

Maybe better use ETH_ALEN instead of magic number?

baruch

>  		for (i = 0; i < bytes / 2; i++)
>  			swap(buf[i], buf[bytes - i - 1]);
>  
> diff --git a/drivers/nvmem/imx-ocotp.c b/drivers/nvmem/imx-ocotp.c
> index 79dd4fda0329..63e9974d9618 100644
> --- a/drivers/nvmem/imx-ocotp.c
> +++ b/drivers/nvmem/imx-ocotp.c
> @@ -228,6 +228,8 @@ static int imx_ocotp_cell_pp(void *context, const char *id, int index,
>  
>  	/* Deal with some post processing of nvmem cell data */
>  	if (id && !strcmp(id, "mac-address"))
> +		if (bytes > 6)
> +			bytes = 6;
>  		for (i = 0; i < bytes / 2; i++)
>  			swap(buf[i], buf[bytes - i - 1]);

-- 
                                                     ~. .~   Tk Open Systems
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   - baruch@...s.co.il - tel: +972.52.368.4656, http://www.tkos.co.il -