linux-kernel - [PATCH] fbdev: via: Fix potential divide by zero

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Message-Id: <20250614005428.3112421-1-alexguo1023@gmail.com>
Date: Fri, 13 Jun 2025 20:54:28 -0400
From: Alex Guo <alexguo1023@...il.com>
To: deller@....de,
	FlorianSchandinat@....de
Cc: alexguo1023@...il.com,
	linux-fbdev@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] fbdev: via: Fix potential divide by zero

Variable var->pixclock can be set by user. In case it equals to
zero, divide by zero would occur in viafb_dvi_set_mode. Similar
crashes have happened in other fbdev drivers. We fix this by
checking whether 'pixclock' is zero.

Signed-off-by: Alex Guo <alexguo1023@...il.com>
---
 drivers/video/fbdev/via/dvi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/via/dvi.c b/drivers/video/fbdev/via/dvi.c
index 27990a73bfa3..0ba248b7b360 100644
--- a/drivers/video/fbdev/via/dvi.c
+++ b/drivers/video/fbdev/via/dvi.c
@@ -166,7 +166,7 @@ void viafb_dvi_set_mode(const struct fb_var_screeninfo *var,
 	int maxPixelClock;
 
 	maxPixelClock = viaparinfo->shared->tmds_setting_info.max_pixel_clock;
-	if (maxPixelClock && PICOS2KHZ(var->pixclock) / 1000 > maxPixelClock) {
+	if (maxPixelClock && var->pixclock && PICOS2KHZ(var->pixclock) / 1000 > maxPixelClock) {
 		rb_mode = viafb_get_best_rb_mode(var->xres, var->yres, 60);
 		if (rb_mode)
 			viafb_fill_var_timing_info(&dvi_var, rb_mode);
-- 
2.34.1