This is a note to let you know that I've just added the patch titled
video: fbdev: asiliantfb: Error out if 'pixclock' equals zero
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
video-fbdev-asiliantfb-error-out-if-pixclock-equals-.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 5f13799011f947070deca2d1f243c5e714484492
Author: Zheyu Ma <zheyuma97@xxxxxxxxx>
Date: Mon Jul 26 10:03:53 2021 +0000
video: fbdev: asiliantfb: Error out if 'pixclock' equals zero
[ 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>
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;
