Re: [PATCH v3] nvmem: imx-ocotp: fix MAC address byte length

[Alexander Stein <alexander.stein@ew.tq-group.com>]

Am Montag, 23. Juni 2025, 19:09:55 CEST schrieb Steffen Bätz:
> 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@vger.kernel.org
> Signed-off-by: Steffen Bätz <steffen@innosonix.de>

Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com>

Thanks

> ---
> v3:
> - replace magic number 6 with ETH_ALEN
> - Fix misleading indentation and properly group 'mac-address' statements
> v2:
> - Add Cc: stable@vger.kernel.org as requested by Greg KH's patch bot
>  drivers/nvmem/imx-ocotp-ele.c | 6 +++++-
>  drivers/nvmem/imx-ocotp.c     | 6 +++++-
>  2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvmem/imx-ocotp-ele.c b/drivers/nvmem/imx-ocotp-ele.c
> index ca6dd71d8a2e..9ef01c91dfa6 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 +119,12 @@ 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")) {
> +		if (bytes > ETH_ALEN)
> +			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..1343cafc37cc 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 +228,12 @@ 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")) {
> +		if (bytes > ETH_ALEN)
> +			bytes = ETH_ALEN;
>  		for (i = 0; i < bytes / 2; i++)
>  			swap(buf[i], buf[bytes - i - 1]);
> +	}
>  
>  	return 0;
>  }
> 


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