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

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Message-Id: <20250614010318.3128558-1-alexguo1023@gmail.com>
Date: Fri, 13 Jun 2025 21:03:18 -0400
From: Alex Guo <alexguo1023@...il.com>
To: deller@....de
Cc: FlorianSchandinat@....de,
	alexguo1023@...il.com,
	linux-fbdev@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] fbdev: via: hw: 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_fill_crtc_timing.
Similar crashes have happened in other fbdev drivers. We fix this
by checking whether '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/via/hw.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/video/fbdev/via/hw.c b/drivers/video/fbdev/via/hw.c
index 66afd7be00cc..31e0cac91889 100644
--- a/drivers/video/fbdev/via/hw.c
+++ b/drivers/video/fbdev/via/hw.c
@@ -1488,8 +1488,9 @@ void viafb_fill_crtc_timing(const struct fb_var_screeninfo *var,
 	if (viaparinfo->chip_info->gfx_chip_name != UNICHROME_CLE266
 		&& viaparinfo->chip_info->gfx_chip_name != UNICHROME_K400)
 		viafb_load_FIFO_reg(iga, var->xres, var->yres);
-
-	viafb_set_vclock(PICOS2KHZ(var->pixclock) * 1000, iga);
+	
+	if (var->pixclock)
+		viafb_set_vclock(PICOS2KHZ(var->pixclock) * 1000, iga);
 }
 
 void viafb_init_chip_info(int chip_type)
-- 
2.34.1