linux-kernel - [PATCH] video: fbdev: sis: Error out if pixclock equals zero

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Date: Thu, 18 Jan 2024 14:24:43 +0800
From: Fullway Wang <fullwaywang@...look.com>
To: deller@....de,
	tzimmermann@...e.de,
	sam@...nborg.org,
	javierm@...hat.com
Cc: linux-fbdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	fullwaywang@...cent.com,
	Fullway Wang <fullwaywang@...look.com>
Subject: [PATCH] video: fbdev: sis: Error out if pixclock equals zero

The userspace program could pass any values to the driver through
ioctl() interface. If the driver doesn't check the value of pixclock,
it may cause divide-by-zero error.

In sisfb_check_var(), var->pixclock is used as a divisor to caculate
drate before it is checked against zero. Fix this by checking it
at the beginning.

This is similar to CVE-2022-3061 in i740fb which was fixed by
commit 15cf0b8.

Signed-off-by: Fullway Wang <fullwaywang@...look.com>
---
 drivers/video/fbdev/sis/sis_main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/video/fbdev/sis/sis_main.c b/drivers/video/fbdev/sis/sis_main.c
index 803ccb6aa479..009bf1d92644 100644
--- a/drivers/video/fbdev/sis/sis_main.c
+++ b/drivers/video/fbdev/sis/sis_main.c
@@ -1444,6 +1444,8 @@ sisfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
 
 	vtotal = var->upper_margin + var->lower_margin + var->vsync_len;
 
+	if (!var->pixclock)
+		return -EINVAL;
 	pixclock = var->pixclock;
 
 	if((var->vmode & FB_VMODE_MASK) == FB_VMODE_NONINTERLACED) {
-- 
2.39.3 (Apple Git-145)