[PATCH] fbdev: udlfb: avoid divide-by-zero on FBIOPUT_VSCREENINFO

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

Much like commit 19f953e74356 ("fbdev: fb_pm2fb: Avoid potential divide
by zero error"), we also need to prevent that same crash from happening
in the udlfb driver as it uses pixclock directly when dividing, which
will crash.

Cc: Bernie Thompson <bernie@plugable.com>
Cc: Helge Deller <deller@gmx.de>
Fixes: 59277b679f8b ("Staging: udlfb: add dynamic modeset support")
Assisted-by: gregkh_clanker_t1000
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/video/fbdev/udlfb.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/video/fbdev/udlfb.c b/drivers/video/fbdev/udlfb.c
index 3c6a9b5758d9..c341d76bc564 100644
--- a/drivers/video/fbdev/udlfb.c
+++ b/drivers/video/fbdev/udlfb.c
@@ -1018,6 +1018,9 @@ static int dlfb_ops_check_var(struct fb_var_screeninfo *var,
 	struct fb_videomode mode;
 	struct dlfb_data *dlfb = info->par;
 
+	if (!var->pixclock)
+		return -EINVAL;
+
 	/* set device-specific elements of var unrelated to mode */
 	dlfb_var_color_format(var);
 
-- 
2.53.0