From d5ba1a855838ea59cbe2e17d2f9ab755d658fdff Mon Sep 17 00:00:00 2001
From: Zheyu Ma <zheyuma97@gmail.com>
Date: Mon, 26 Jul 2021 10:03:54 +0000
Subject: video: fbdev: kyro: Error out if 'pixclock' equals zero
Git-commit: 1520b4b7ba964f8eec2e7dd14c571d50de3e5191
Patch-mainline: v5.15-rc1
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 because the value of 'lineclock' and
'frameclock' will be zero.
Fix this by checking whether 'pixclock' is zero in kyrofb_check_var().
The following log reveals it:
[ 103.073930] divide error: 0000 [#1] PREEMPT SMP KASAN PTI
[ 103.073942] CPU: 4 PID: 12483 Comm: syz-executor Not tainted 5.14.0-rc2-00478-g2734d6c1b1a0-dirty #118
[ 103.073959] RIP: 0010:kyrofb_set_par+0x316/0xc80
[ 103.074045] Call Trace:
[ 103.074048] ? ___might_sleep+0x1ee/0x2d0
[ 103.074060] ? kyrofb_ioctl+0x330/0x330
[ 103.074069] fb_set_var+0x5bf/0xeb0
[ 103.074078] ? fb_blank+0x1a0/0x1a0
[ 103.074085] ? lock_acquire+0x3bd/0x530
[ 103.074094] ? lock_release+0x810/0x810
[ 103.074103] ? ___might_sleep+0x1ee/0x2d0
[ 103.074114] ? __mutex_lock+0x620/0x1190
[ 103.074126] ? trace_hardirqs_on+0x6a/0x1c0
[ 103.074137] do_fb_ioctl+0x31e/0x700
[ 103.074144] ? fb_getput_cmap+0x280/0x280
[ 103.074152] ? rcu_read_lock_sched_held+0x11/0x80
[ 103.074162] ? rcu_read_lock_sched_held+0x11/0x80
[ 103.074171] ? __sanitizer_cov_trace_switch+0x67/0xf0
[ 103.074181] ? __sanitizer_cov_trace_const_cmp2+0x20/0x80
[ 103.074191] ? do_vfs_ioctl+0x14b/0x16c0
[ 103.074199] ? vfs_fileattr_set+0xb60/0xb60
[ 103.074207] ? rcu_read_lock_sched_held+0x11/0x80
[ 103.074216] ? lock_release+0x483/0x810
[ 103.074224] ? __fget_files+0x217/0x3d0
[ 103.074234] ? __fget_files+0x239/0x3d0
[ 103.074243] ? do_fb_ioctl+0x700/0x700
[ 103.074250] fb_ioctl+0xe6/0x130
Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1627293835-17441-3-git-send-email-zheyuma97@gmail.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/video/fbdev/kyro/fbdev.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/video/fbdev/kyro/fbdev.c b/drivers/video/fbdev/kyro/fbdev.c
index 4b8c7c16b1df..25801e8e3f74 100644
--- a/drivers/video/fbdev/kyro/fbdev.c
+++ b/drivers/video/fbdev/kyro/fbdev.c
@@ -399,6 +399,9 @@ static int kyrofb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
{
struct kyrofb_info *par = info->par;
+ if (!var->pixclock)
+ return -EINVAL;
+
if (var->bits_per_pixel != 16 && var->bits_per_pixel != 32) {
printk(KERN_WARNING "kyrofb: depth not supported: %u\n", var->bits_per_pixel);
return -EINVAL;
--
2.38.1