usb: gadget: configfs: Ignore trailing LF for user strings to cdev

BugLink: https://bugs.launchpad.net/bugs/2106770

commit 9466545 upstream.

Since commit c033563
("usb: gadget: configfs: Attach arbitrary strings to cdev")
a user can provide extra string descriptors to a USB gadget via configfs.

For "manufacturer", "product", "serialnumber", setting the string via
configfs ignores a trailing LF.

For the arbitrary strings the LF was not ignored.

This patch ignores a trailing LF to make this consistent with the existing
behavior for "manufacturer", ...  string descriptors.

Fixes: c033563 ("usb: gadget: configfs: Attach arbitrary strings to cdev")
Cc: stable <stable@kernel.org>
Signed-off-by: Ingo Rohloff <ingo.rohloff@lauterbach.com>
Link: https://lore.kernel.org/r/20241212154114.29295-1-ingo.rohloff@lauterbach.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Manuel Diewald <manuel.diewald@canonical.com>
Signed-off-by: Mehmet Basaran <mehmet.basaran@canonical.com>

Author: trace32

drivers/usb/gadget/configfs.c

@@ -827,11 +827,15 @@ static ssize_t gadget_string_s_store(struct config_item *item, const char *page,
 {
 	struct gadget_string *string = to_gadget_string(item);
 	int size = min(sizeof(string->string), len + 1);
+	ssize_t cpy_len;
 
 	if (len > USB_MAX_STRING_LEN)
 		return -EINVAL;
 
-	return strscpy(string->string, page, size);
+	cpy_len = strscpy(string->string, page, size);
+	if (cpy_len > 0 && string->string[cpy_len - 1] == '\n')
+		string->string[cpy_len - 1] = 0;
+	return len;
 }
 CONFIGFS_ATTR(gadget_string_, s);