linux-kernel - [PATCH v2] usb: replace hardcode maximum usb string length by definition

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Message-ID: <1592201855-8218-1-git-send-email-macpaul.lin@mediatek.com>
Date:   Mon, 15 Jun 2020 14:17:35 +0800
From:   Macpaul Lin <macpaul.lin@...iatek.com>
To:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.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>,
        Alan Stern <stern@...land.harvard.edu>
CC:     Mediatek WSD Upstream <wsd_upstream@...iatek.com>,
        Macpaul Lin <macpaul.lin@...iatek.com>,
        Macpaul Lin <macpaul.lin@...il.com>
Subject: [PATCH v2] usb: replace hardcode maximum usb string length by definition

Replace hardcode maximum usb string length (126 bytes) by definition
"MAX_USB_STRING_LEN".

Signed-off-by: Macpaul Lin <macpaul.lin@...iatek.com>
---
Changes for v2:
  - Add definition "MAX_USB_STRING_LEN" in ch9.h instead of in usb.h.
    Thanks for Alan's suggestion.

 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
+
 /* USB_DT_STRING: String descriptor */
 struct usb_string_descriptor {
 	__u8  bLength;
-- 
1.7.9.5