From 2a70ab783de5af73c7c6f6270bbfc51844210b3b Mon Sep 17 00:00:00 2001
From: Zheyu Ma <zheyuma97@gmail.com>
Date: Mon, 26 Jul 2021 10:03:53 +0000
Subject: [PATCH] video: fbdev: asiliantfb: Error out if 'pixclock' equals zero
Git-commit: b36b242d4b8ea178f7fd038965e3cac7f30c3f09
Patch-mainline: v5.15-rc1
References: stable-5.14.6
[ Upstream commit b36b242d4b8ea178f7fd038965e3cac7f30c3f09 ]
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 first.
The following log reveals it:
[ 43.861711] divide error: 0000 [#1] PREEMPT SMP KASAN PTI
[ 43.861737] CPU: 2 PID: 11764 Comm: i740 Not tainted 5.14.0-rc2-00513-gac532c9bbcfb-dirty #224
[ 43.861756] RIP: 0010:asiliantfb_check_var+0x4e/0x730
[ 43.861843] Call Trace:
[ 43.861848] ? asiliantfb_remove+0x190/0x190
[ 43.861858] fb_set_var+0x2e4/0xeb0
[ 43.861866] ? fb_blank+0x1a0/0x1a0
[ 43.861873] ? lock_acquire+0x1ef/0x530
[ 43.861884] ? lock_release+0x810/0x810
[ 43.861892] ? lock_is_held_type+0x100/0x140
[ 43.861903] ? ___might_sleep+0x1ee/0x2d0
[ 43.861914] ? __mutex_lock+0x620/0x1190
[ 43.861921] ? do_fb_ioctl+0x313/0x700
[ 43.861929] ? mutex_lock_io_nested+0xfa0/0xfa0
[ 43.861936] ? __this_cpu_preempt_check+0x1d/0x30
[ 43.861944] ? _raw_spin_unlock_irqrestore+0x46/0x60
[ 43.861952] ? lockdep_hardirqs_on+0x59/0x100
[ 43.861959] ? _raw_spin_unlock_irqrestore+0x46/0x60
[ 43.861967] ? trace_hardirqs_on+0x6a/0x1c0
[ 43.861978] 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/1627293835-17441-2-git-send-email-zheyuma97@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/video/fbdev/asiliantfb.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/video/fbdev/asiliantfb.c b/drivers/video/fbdev/asiliantfb.c
index 3e006da47752..84c56f525889 100644
--- a/drivers/video/fbdev/asiliantfb.c
+++ b/drivers/video/fbdev/asiliantfb.c
@@ -227,6 +227,9 @@ static int asiliantfb_check_var(struct fb_var_screeninfo *var,
{
unsigned long Ftarget, ratio, remainder;
+ if (!var->pixclock)
+ return -EINVAL;
+
ratio = 1000000 / var->pixclock;
remainder = 1000000 % var->pixclock;
Ftarget = 1000000 * ratio + (1000000 * remainder) / var->pixclock;
--
2.26.2