From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Thu, 9 Apr 2026 13:23:46 +0000 (+0200)
Subject: fbdev: udlfb: avoid divide-by-zero on FBIOPUT_VSCREENINFO
X-Git-Tag: v6.19.14~52
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cccbf9b7fdab48ce4feb69c24f7f928aa8e4e8b8;p=thirdparty%2Fkernel%2Fstable.git

fbdev: udlfb: avoid divide-by-zero on FBIOPUT_VSCREENINFO

commit a31e4518bec70333a0a98f2946a12b53b45fe5b9 upstream.

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>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/video/fbdev/udlfb.c b/drivers/video/fbdev/udlfb.c
index ccede85df1e1..28e6d75e13ed 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);