linux-kernel - [PATCH AUTOSEL 4.19 3/5] fbdev: savage: Error out if pixclock equals zero

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Date: Fri,  2 Feb 2024 13:42:24 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Fullway Wang <fullwaywang@...look.com>,
	Helge Deller <deller@....de>,
	Sasha Levin <sashal@...nel.org>,
	adaplas@...il.com,
	linux-fbdev@...r.kernel.org,
	dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 4.19 3/5] fbdev: savage: Error out if pixclock equals zero

From: Fullway Wang <fullwaywang@...look.com>

[ Upstream commit 04e5eac8f3ab2ff52fa191c187a46d4fdbc1e288 ]

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.

Although pixclock is checked in savagefb_decode_var(), but it is not
checked properly in savagefb_probe(). Fix this by checking whether
pixclock is zero in the function savagefb_check_var() before
info->var.pixclock is used as the divisor.

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

Signed-off-by: Fullway Wang <fullwaywang@...look.com>
Signed-off-by: Helge Deller <deller@....de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/video/fbdev/savage/savagefb_driver.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/video/fbdev/savage/savagefb_driver.c b/drivers/video/fbdev/savage/savagefb_driver.c
index c09d7426cd92..d9eafdb89cea 100644
--- a/drivers/video/fbdev/savage/savagefb_driver.c
+++ b/drivers/video/fbdev/savage/savagefb_driver.c
@@ -869,6 +869,9 @@ static int savagefb_check_var(struct fb_var_screeninfo   *var,
 
 	DBG("savagefb_check_var");
 
+	if (!var->pixclock)
+		return -EINVAL;
+
 	var->transp.offset = 0;
 	var->transp.length = 0;
 	switch (var->bits_per_pixel) {
-- 
2.43.0