Re: [PATCH v3] usb: gadget: f_ncm: Fix MAC assignment NCM ethernet

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Aug 14, 2025 at 11:50:51AM -0400, raub camaioni wrote:
> This fix is already present in f_ecm.c and was never
> propagated to f_ncm.c
> 
> When creating multiple NCM ethernet devices
> on a composite usb gadget device
> each MAC address on the HOST side will be identical.
> Having the same MAC on different network interfaces is bad.
> 
> This fix updates the MAC address inside the
> ncm_strings_defs global during the ncm_bind call.
> This ensures each device has a unique MAC.
> In f_ecm.c ecm_string_defs is updated in the same way.
> 
> The defunct MAC assignment in ncm_alloc has been removed.
> 
> Signed-off-by: raub camaioni <raubcameo@gmail.com>
> ---
>  drivers/usb/gadget/function/f_ncm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/function/f_ncm.c b/drivers/usb/gadget/function/f_ncm.c
> index 58b0dd575af3..186fbb9d0a3d 100644
> --- a/drivers/usb/gadget/function/f_ncm.c
> +++ b/drivers/usb/gadget/function/f_ncm.c
> @@ -1463,6 +1463,8 @@ static int ncm_bind(struct usb_configuration *c, struct usb_function *f)
>  
>  	ncm_opts->bound = true;
>  
> +	ncm_string_defs[1].s = ecm->ethaddr;
> +
>  	us = usb_gstrings_attach(cdev, ncm_strings,
>  				 ARRAY_SIZE(ncm_string_defs));
>  	if (IS_ERR(us)) {
> @@ -1771,7 +1773,6 @@ static struct usb_function *ncm_alloc(struct usb_function_instance *fi)
>  		mutex_unlock(&opts->lock);
>  		return ERR_PTR(-EINVAL);
>  	}
> -	ncm_string_defs[STRING_MAC_IDX].s = ncm->ethaddr;
>  
>  	spin_lock_init(&ncm->lock);
>  	ncm_reset_values(ncm);
> -- 
> 2.34.1
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
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  Please read the section entitled "The canonical patch format" in the
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If you wish to discuss this problem further, or you have questions about
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thanks,

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