[PATCH 4.14 146/217] video: fbdev: asiliantfb: Error out if pixclock equals zero
From: Greg Kroah-Hartman
Date: Mon Sep 20 2021 - 13:28:49 EST
From: Zheyu Ma <zheyuma97@xxxxxxxxx>
[ 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@xxxxxxxxx>
Signed-off-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/1627293835-17441-2-git-send-email-zheyuma97@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 ea31054a28ca..c1d6e6336225 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;
--
2.30.2