[PATCH 5.10 071/355] fbdev: core: fbcvt: avoid division by 0 in fb_cvt_hperiod()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sergey Shtylyov <s.shtylyov@omp.ru>

[ Upstream commit 3f6dae09fc8c306eb70fdfef70726e1f154e173a ]

In fb_find_mode_cvt(), iff mode->refresh somehow happens to be 0x80000000,
cvt.f_refresh will become 0 when multiplying it by 2 due to overflow. It's
then passed to fb_cvt_hperiod(), where it's used as a divider -- division
by 0 will result in kernel oops. Add a sanity check for cvt.f_refresh to
avoid such overflow...

Found by Linux Verification Center (linuxtesting.org) with the Svace static
analysis tool.

Fixes: 96fe6a2109db ("[PATCH] fbdev: Add VESA Coordinated Video Timings (CVT) support")
Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/video/fbdev/core/fbcvt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/core/fbcvt.c b/drivers/video/fbdev/core/fbcvt.c
index 64843464c6613..cd3821bd82e56 100644
--- a/drivers/video/fbdev/core/fbcvt.c
+++ b/drivers/video/fbdev/core/fbcvt.c
@@ -312,7 +312,7 @@ int fb_find_mode_cvt(struct fb_videomode *mode, int margins, int rb)
 	cvt.f_refresh = cvt.refresh;
 	cvt.interlace = 1;
 
-	if (!cvt.xres || !cvt.yres || !cvt.refresh) {
+	if (!cvt.xres || !cvt.yres || !cvt.refresh || cvt.f_refresh > INT_MAX) {
 		printk(KERN_INFO "fbcvt: Invalid input parameters\n");
 		return 1;
 	}
-- 
2.39.5