drm/gma500: Remove VLA

There's an ongoing effort to remove VLAs[1] from the kernel to eventually
turn on -Wvla. Switch to a reasonable upper bound for the VLAs in
the gma500 driver.

[1] https://lkml.org/lkml/2018/3/7/621Signed-off-by: Laura Abbott <labbott@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180409210647.3718-1-labbott@redhat.com

drivers/gpu/drm/gma500/psb_intel_sdvo.c

@@ -429,13 +429,20 @@ static const char *cmd_status_names[] = {
 	"Scaling not supported"
 };
 
+#define MAX_ARG_LEN 32
+
 static bool psb_intel_sdvo_write_cmd(struct psb_intel_sdvo *psb_intel_sdvo, u8 cmd,
 				 const void *args, int args_len)
 {
-	u8 buf[args_len*2 + 2], status;
-	struct i2c_msg msgs[args_len + 3];
+	u8 buf[MAX_ARG_LEN*2 + 2], status;
+	struct i2c_msg msgs[MAX_ARG_LEN + 3];
 	int i, ret;
 
+	if (args_len > MAX_ARG_LEN) {
+		DRM_ERROR("Need to increase arg length\n");
+		return false;
+	}
+
 	psb_intel_sdvo_debug_write(psb_intel_sdvo, cmd, args, args_len);
 
 	for (i = 0; i < args_len; i++) {