video: hdmi: prefer length specifier in format over string copying

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

It looks like the main use of strncpy() here is to limit the amount of
bytes printed from hdmi_log() by using a tmp buffer and limiting the
number of bytes copied. Really, we should use the %.<len>s format
qualifier to achieve this.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/drivers/video/hdmi.c b/drivers/video/hdmi.c
index 03c7f27dde4951e9078c406f21c75d399bcdacd8..ba301f3f4951ed74b4b771ce76a75d0e832d684b 100644 (file)
--- a/drivers/video/hdmi.c
+++ b/drivers/video/hdmi.c
@@ -1310,17 +1310,11 @@ static void hdmi_spd_infoframe_log(const char *level,
                                   struct device *dev,
                                   const struct hdmi_spd_infoframe *frame)
 {
-       u8 buf[17];
-
        hdmi_infoframe_log_header(level, dev,
                                  (const struct hdmi_any_infoframe *)frame);
 
-       memset(buf, 0, sizeof(buf));
-
-       strncpy(buf, frame->vendor, 8);
-       hdmi_log("    vendor: %s\n", buf);
-       strncpy(buf, frame->product, 16);
-       hdmi_log("    product: %s\n", buf);
+       hdmi_log("    vendor: %.8s\n", frame->vendor);
+       hdmi_log("    product: %.16s\n", frame->product);
        hdmi_log("    source device information: %s (0x%x)\n",
                hdmi_spd_sdi_get_name(frame->sdi), frame->sdi);
 }