From: Zheyu Ma zheyuma97@gmail.com

[ 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-em... Signed-off-by: Sasha Levin sashal@kernel.org --- 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;