From 2b6a5c785dcf03279655c46527aeac4116162a2a Mon Sep 17 00:00:00 2001
From: Zheyu Ma <zheyuma97@gmail.com>
Date: Mon, 4 Apr 2022 16:47:21 +0800
Subject: video: fbdev: tridentfb: Error out if 'pixclock' equals zero
Git-commit: 16844e5870424c2728486dc0c0300ebf7fa09ad6
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 'pixclock',
it may cause divide error.
Fix this by checking whether 'pixclock' is zero.
The following log reveals it:
divide error: 0000 [#1] PREEMPT SMP KASAN PTI
RIP: 0010:tridentfb_check_var+0x853/0xe60
Call Trace:
<TASK>
fb_set_var+0x367/0xeb0
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/tridentfb.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/video/fbdev/tridentfb.c b/drivers/video/fbdev/tridentfb.c
index 4d20cb557ff0..319131bd72cf 100644
--- a/drivers/video/fbdev/tridentfb.c
+++ b/drivers/video/fbdev/tridentfb.c
@@ -996,6 +996,9 @@ static int tridentfb_check_var(struct fb_var_screeninfo *var,
int ramdac = 230000; /* 230MHz for most 3D chips */
debug("enter\n");
+ if (!var->pixclock)
+ return -EINVAL;
+
/* check color depth */
if (bpp == 24)
bpp = var->bits_per_pixel = 32;
--
2.38.1