linux-kernel - [PATCH] fbdev: i810 Fix potential divide by zero

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Message-Id: <20250614052629.3549586-1-alexguo1023@gmail.com>
Date: Sat, 14 Jun 2025 01:26:29 -0400
From: Alex Guo <alexguo1023@...il.com>
To: deller@....de
Cc: alexguo1023@...il.com,
	linux-fbdev@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] fbdev: i810 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 i810fb_fill_var_timings and
i810_get_watermark.
We cannot find the default valid value of pixclock for driver
i810, so we fix this by returning directly if 'pixclock' is
zero.

Similar commit: commit 16844e58704 ("video: fbdev: tridentfb:
Error out if 'pixclock' equals zero")

Signed-off-by: Alex Guo <alexguo1023@...il.com>
---
 drivers/video/fbdev/i810/i810_dvt.c | 2 ++
 drivers/video/fbdev/i810/i810_gtf.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/drivers/video/fbdev/i810/i810_dvt.c b/drivers/video/fbdev/i810/i810_dvt.c
index 2082b5c92e8f..1db4a63a2631 100644
--- a/drivers/video/fbdev/i810/i810_dvt.c
+++ b/drivers/video/fbdev/i810/i810_dvt.c
@@ -251,6 +251,8 @@ void i810fb_fill_var_timings(struct fb_var_screeninfo *var)
 	xres = var->xres;
 	yres = var->yres;
 	
+	if (!var->pixclock)
+		return;
 	pixclock = 1000000000 / var->pixclock;
 	mode = i810fb_find_best_mode(xres, yres, pixclock);
 	
diff --git a/drivers/video/fbdev/i810/i810_gtf.c b/drivers/video/fbdev/i810/i810_gtf.c
index 9743d51e7f8c..ae001b256ace 100644
--- a/drivers/video/fbdev/i810/i810_gtf.c
+++ b/drivers/video/fbdev/i810/i810_gtf.c
@@ -259,6 +259,8 @@ u32 i810_get_watermark(const struct fb_var_screeninfo *var,
 		}
 	}
 
+	if (!var->pixclock)
+		return -EINVAL;
 	pixclock = 1000000/var->pixclock;
 	min = ~0;
 	for (i = 0; i < size; i++) {
-- 
2.34.1