From feef7362428c98bed72cc935c88c2a233f973e95 Mon Sep 17 00:00:00 2001
From: Zheyu Ma <zheyuma97@gmail.com>
Date: Mon, 4 Apr 2022 16:47:19 +0800
Subject: video: fbdev: kyro: Error out if 'lineclock' equals zero
Git-commit: 213e2df4733275165038d77289812d4473b0b010
Patch-mainline: v5.18-rc5
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

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

Fix this by checking whether 'lineclock' is zero.

The following log reveals it:
 divide error: 0000 [#1] PREEMPT SMP KASAN PTI
 RIP: 0010:kyrofb_set_par+0x30d/0xd80
 Call Trace:
  <TASK>
  fb_set_var+0x604/0xeb0
  do_fb_ioctl+0x234/0x670
  fb_ioctl+0xdd/0x130
  do_syscall_64+0x3b/0x90

Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/video/fbdev/kyro/fbdev.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/video/fbdev/kyro/fbdev.c b/drivers/video/fbdev/kyro/fbdev.c
index 25801e8e3f74..d57772f96ad2 100644
--- a/drivers/video/fbdev/kyro/fbdev.c
+++ b/drivers/video/fbdev/kyro/fbdev.c
@@ -494,6 +494,8 @@ static int kyrofb_set_par(struct fb_info *info)
 				    info->var.hsync_len +
 				    info->var.left_margin)) / 1000;
 
+	if (!lineclock)
+		return -EINVAL;
 
 	/* time for a frame in ns (precision in 32bpp) */
 	frameclock = lineclock * (info->var.yres +
-- 
2.38.1