From 05fad67bb4cf8694a0815ddc355cb6346fb61dcc Mon Sep 17 00:00:00 2001
From: Zheyu Ma <zheyuma97@gmail.com>
Date: Mon, 4 Apr 2022 16:47:23 +0800
Subject: video: fbdev: s3fb: Error out if 'pixclock' equals zero
Git-commit: 7015bb57c304bad7289e872c2c5c587adee3a756
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 in s3fb_check_var().
The following log reveals it:
divide error: 0000 [#1] PREEMPT SMP KASAN PTI
RIP: 0010:s3fb_check_var+0x3f3/0x530
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/s3fb.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/video/fbdev/s3fb.c b/drivers/video/fbdev/s3fb.c
index 5c74253e7b2c..b93c8eb02336 100644
--- a/drivers/video/fbdev/s3fb.c
+++ b/drivers/video/fbdev/s3fb.c
@@ -549,6 +549,9 @@ static int s3fb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
int rv, mem, step;
u16 m, n, r;
+ if (!var->pixclock)
+ return -EINVAL;
+
/* Find appropriate format */
rv = svga_match_format (s3fb_formats, var, NULL);
--
2.38.1