From ec75a4111494157734f3d55e5b2f307f5fdd1fe0 Mon Sep 17 00:00:00 2001 From: Zheyu Ma Date: Wed, 21 Jul 2021 12:43:44 +0000 Subject: [PATCH] video: fbdev: neofb: add a check against divide error 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 Signed-off-by: Sam Ravnborg Link: https://patchwork.freedesktop.org/patch/msgid/1626871424-27708-1-git-send-email-zheyuma97@gmail.com --- 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 c0f4f402da3f4..966df2a073606 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? */ -- 2.39.5