usbip: usbip_host: Replace strlcpy with strscpy

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().

Direct replacement is safe here since return value of -errno
is used to check for truncation instead of sizeof(dest).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] KSPP#89

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Message-ID: <20230615180504.401169-1-azeemshaikh38@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: azeemshaikh38

drivers/usb/usbip/stub_main.c

@@ -167,15 +167,13 @@ static ssize_t match_busid_show(struct device_driver *drv, char *buf)
 static ssize_t match_busid_store(struct device_driver *dev, const char *buf,
 				 size_t count)
 {
-	int len;
 	char busid[BUSID_SIZE];
 
 	if (count < 5)
 		return -EINVAL;
 
 	/* busid needs to include \0 termination */
-	len = strlcpy(busid, buf + 4, BUSID_SIZE);
-	if (sizeof(busid) <= len)
+	if (strscpy(busid, buf + 4, BUSID_SIZE) < 0)
 		return -EINVAL;
 
 	if (!strncmp(buf, "add ", 4)) {