From f02a46bdfc1b8c39f65ff92ac24be0ad9e595bff Mon Sep 17 00:00:00 2001
From: Zheyu Ma <zheyuma97@gmail.com>
Date: Wed, 21 Jul 2021 12:43:44 +0000
Subject: video: fbdev: neofb: add a check against divide error
Git-commit: 030fadb0138186cfa04492e1132a9df514d03841
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 of the 'PICOS2KHZ' macro.
Fix this by checking whether 'pixclock' is zero first.
The following log reveals it:
[ 53.093806] divide error: 0000 [#1] PREEMPT SMP KASAN PTI
[ 53.093838] CPU: 3 PID: 11763 Comm: hang Not tainted 5.14.0-rc2-00478-g2734d6c1b1a0 #215
[ 53.093859] RIP: 0010:neofb_check_var+0x80/0xe50
[ 53.093951] Call Trace:
[ 53.093956] ? neofb_setcolreg+0x2b0/0x2b0
[ 53.093968] fb_set_var+0x2e4/0xeb0
[ 53.093977] ? fb_blank+0x1a0/0x1a0
[ 53.093984] ? lock_acquire+0x1ef/0x530
[ 53.093996] ? lock_release+0x810/0x810
[ 53.094005] ? lock_is_held_type+0x100/0x140
[ 53.094016] ? ___might_sleep+0x1ee/0x2d0
[ 53.094028] ? __mutex_lock+0x620/0x1190
[ 53.094036] ? do_fb_ioctl+0x313/0x700
[ 53.094044] ? mutex_lock_io_nested+0xfa0/0xfa0
[ 53.094051] ? __this_cpu_preempt_check+0x1d/0x30
[ 53.094060] ? _raw_spin_unlock_irqrestore+0x46/0x60
[ 53.094069] ? lockdep_hardirqs_on+0x59/0x100
[ 53.094076] ? _raw_spin_unlock_irqrestore+0x46/0x60
[ 53.094085] ? trace_hardirqs_on+0x6a/0x1c0
[ 53.094096] do_fb_ioctl+0x31e/0x700
Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1626871424-27708-1-git-send-email-zheyuma97@gmail.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/video/fbdev/neofb.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/neofb.c b/drivers/video/fbdev/neofb.c
index c0f4f402da3f..966df2a07360 100644
--- a/drivers/video/fbdev/neofb.c
+++ b/drivers/video/fbdev/neofb.c
@@ -585,7 +585,7 @@ neofb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
DBG("neofb_check_var");
- if (PICOS2KHZ(var->pixclock) > par->maxClock)
+ if (var->pixclock && PICOS2KHZ(var->pixclock) > par->maxClock)
return -EINVAL;
/* Is the mode larger than the LCD panel? */
--
2.38.1