linux-kernel - Re: [PATCH v3] usb: replace hardcode maximum usb string length by definition

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Date:   Thu, 18 Jun 2020 16:02:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Macpaul Lin <macpaul.lin@...iatek.com>
Cc:     Alan Stern <stern@...land.harvard.edu>,
        Felipe Balbi <balbi@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, Jim Lin <jilin@...dia.com>,
        Siqi Lin <siqilin@...gle.com>,
        Mediatek WSD Upstream <wsd_upstream@...iatek.com>,
        Macpaul Lin <macpaul.lin@...il.com>
Subject: Re: [PATCH v3] usb: replace hardcode maximum usb string length by
 definition

On Thu, Jun 18, 2020 at 05:13:38PM +0800, Macpaul Lin wrote:
> Replace hardcode maximum usb string length (126 bytes) by definition
> "MAX_USB_STRING_LEN".
> 
> Signed-off-by: Macpaul Lin <macpaul.lin@...iatek.com>
> Acked-by: Alan Stern <stern@...land.harvard.edu>
> ---
> Changes for v2:
>   - Add definition "MAX_USB_STRING_LEN" in ch9.h instead of in usb.h.
>     Thanks for Alan's suggestion.
> Changes for v3:
>   - Rebase to 5.8-rc1 and resolve conflict.
> 
>  drivers/usb/gadget/composite.c |    4 ++--
>  drivers/usb/gadget/configfs.c  |    2 +-
>  drivers/usb/gadget/usbstring.c |    4 ++--
>  include/uapi/linux/usb/ch9.h   |    3 +++
>  4 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> index cb4950c..d0de016 100644
> --- a/drivers/usb/gadget/composite.c
> +++ b/drivers/usb/gadget/composite.c
> @@ -1041,7 +1041,7 @@ static void collect_langs(struct usb_gadget_strings **sp, __le16 *buf)
>  	while (*sp) {
>  		s = *sp;
>  		language = cpu_to_le16(s->language);
> -		for (tmp = buf; *tmp && tmp < &buf[126]; tmp++) {
> +		for (tmp = buf; *tmp && tmp < &buf[MAX_USB_STRING_LEN]; tmp++) {
>  			if (*tmp == language)
>  				goto repeat;
>  		}
> @@ -1116,7 +1116,7 @@ static int get_string(struct usb_composite_dev *cdev,
>  			collect_langs(sp, s->wData);
>  		}
>  
> -		for (len = 0; len <= 126 && s->wData[len]; len++)
> +		for (len = 0; len <= MAX_USB_STRING_LEN && s->wData[len]; len++)
>  			continue;
>  		if (!len)
>  			return -EINVAL;
> diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c
> index 32b637e..70dd4ba 100644
> --- a/drivers/usb/gadget/configfs.c
> +++ b/drivers/usb/gadget/configfs.c
> @@ -115,7 +115,7 @@ static int usb_string_copy(const char *s, char **s_copy)
>  	char *str;
>  	char *copy = *s_copy;
>  	ret = strlen(s);
> -	if (ret > 126)
> +	if (ret > MAX_USB_STRING_LEN)
>  		return -EOVERFLOW;
>  
>  	str = kstrdup(s, GFP_KERNEL);
> diff --git a/drivers/usb/gadget/usbstring.c b/drivers/usb/gadget/usbstring.c
> index 7c24d1c..8a8d647 100644
> --- a/drivers/usb/gadget/usbstring.c
> +++ b/drivers/usb/gadget/usbstring.c
> @@ -55,9 +55,9 @@
>  		return -EINVAL;
>  
>  	/* string descriptors have length, tag, then UTF16-LE text */
> -	len = min ((size_t) 126, strlen (s->s));
> +	len = min((size_t)MAX_USB_STRING_LEN, strlen(s->s));
>  	len = utf8s_to_utf16s(s->s, len, UTF16_LITTLE_ENDIAN,
> -			(wchar_t *) &buf[2], 126);
> +			(wchar_t *) &buf[2], MAX_USB_STRING_LEN);
>  	if (len < 0)
>  		return -EINVAL;
>  	buf [0] = (len + 1) * 2;
> diff --git a/include/uapi/linux/usb/ch9.h b/include/uapi/linux/usb/ch9.h
> index 2b623f3..cc02d05 100644
> --- a/include/uapi/linux/usb/ch9.h
> +++ b/include/uapi/linux/usb/ch9.h
> @@ -364,6 +364,9 @@ struct usb_config_descriptor {
>  
>  /*-------------------------------------------------------------------------*/
>  
> +/* USB String descriptors can contain at most 126 characters. */
> +#define MAX_USB_STRING_LEN	126

Nit, as this is part of the userspace api, we should make this
"USB_MAX_STRING_LEN" as we should be using "USB_" for all exports here.

That seems to be the case already except for one really odd set of
"TEST_" defines, which I'll go fix up after this...

I will just hand-edit this patch to make that change so you don't have
to respin it again...

thanks,

greg k-h