add checks against divide error

Zheyu Ma (3):
  video: fbdev: kyro: add a check against divide error
  video: fbdev: riva: add a check against divide error
  video: fbdev: asiliantfb: add a check against divide error

 drivers/video/fbdev/asiliantfb.c | 3 +++
 drivers/video/fbdev/kyro/fbdev.c | 3 +++
 drivers/video/fbdev/riva/fbdev.c | 3 +++
 3 files changed, 9 insertions(+)

-- 
2.17.6

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 the value of 'lineclock' and
'frameclock' will be zero.

Fix this by checking whether 'pixclock' is zero in kyrofb_check_var().

The following log reveals it:

[  103.073930] divide error: 0000 [#1] PREEMPT SMP KASAN PTI
[  103.073942] CPU: 4 PID: 12483 Comm: syz-executor Not tainted 5.14.0-rc2-00478-g2734d6c1b1a0-dirty #118
[  103.073959] RIP: 0010:kyrofb_set_par+0x316/0xc80
[  103.074045] Call Trace:
[  103.074048]  ? ___might_sleep+0x1ee/0x2d0
[  103.074060]  ? kyrofb_ioctl+0x330/0x330
[  103.074069]  fb_set_var+0x5bf/0xeb0
[  103.074078]  ? fb_blank+0x1a0/0x1a0
[  103.074085]  ? lock_acquire+0x3bd/0x530
[  103.074094]  ? lock_release+0x810/0x810
[  103.074103]  ? ___might_sleep+0x1ee/0x2d0
[  103.074114]  ? __mutex_lock+0x620/0x1190
[  103.074126]  ? trace_hardirqs_on+0x6a/0x1c0
[  103.074137]  do_fb_ioctl+0x31e/0x700
[  103.074144]  ? fb_getput_cmap+0x280/0x280
[  103.074152]  ? rcu_read_lock_sched_held+0x11/0x80
[  103.074162]  ? rcu_read_lock_sched_held+0x11/0x80
[  103.074171]  ? __sanitizer_cov_trace_switch+0x67/0xf0
[  103.074181]  ? __sanitizer_cov_trace_const_cmp2+0x20/0x80
[  103.074191]  ? do_vfs_ioctl+0x14b/0x16c0
[  103.074199]  ? vfs_fileattr_set+0xb60/0xb60
[  103.074207]  ? rcu_read_lock_sched_held+0x11/0x80
[  103.074216]  ? lock_release+0x483/0x810
[  103.074224]  ? __fget_files+0x217/0x3d0
[  103.074234]  ? __fget_files+0x239/0x3d0
[  103.074243]  ? do_fb_ioctl+0x700/0x700
[  103.074250]  fb_ioctl+0xe6/0x130

Signed-off-by: Zheyu Ma <redacted>
---
 drivers/video/fbdev/kyro/fbdev.c | 3 +++

2 more lines

diff --git a/drivers/video/fbdev/kyro/fbdev.c b/drivers/video/fbdev/kyro/fbdev.c
index 8fbde92ae8b9..6db7e5e83f11 100644
--- a/drivers/video/fbdev/kyro/fbdev.c
+++ b/drivers/video/fbdev/kyro/fbdev.c

@@ -394,6 +394,9 @@ static int kyrofb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
 {
 	struct kyrofb_info *par = info->par;
 
+	if (!var->pixclock)
+		return -EINVAL;
+
 	if (var->bits_per_pixel != 16 && var->bits_per_pixel != 32) {
 		printk(KERN_WARNING "kyrofb: depth not supported: %u\n", var->bits_per_pixel);
 		return -EINVAL;

-- 
2.17.6

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:

[   33.396850] divide error: 0000 [#1] PREEMPT SMP KASAN PTI
[   33.396864] CPU: 5 PID: 11754 Comm: i740 Not tainted 5.14.0-rc2-00513-gac532c9bbcfb-dirty #222
[   33.396883] RIP: 0010:riva_load_video_mode+0x417/0xf70
[   33.396969] Call Trace:
[   33.396973]  ? debug_smp_processor_id+0x1c/0x20
[   33.396984]  ? tick_nohz_tick_stopped+0x1a/0x90
[   33.396996]  ? rivafb_copyarea+0x3c0/0x3c0
[   33.397003]  ? wake_up_klogd.part.0+0x99/0xd0
[   33.397014]  ? vprintk_emit+0x110/0x4b0
[   33.397024]  ? vprintk_default+0x26/0x30
[   33.397033]  ? vprintk+0x9c/0x1f0
[   33.397041]  ? printk+0xba/0xed
[   33.397054]  ? record_print_text.cold+0x16/0x16
[   33.397063]  ? __kasan_check_read+0x11/0x20
[   33.397074]  ? profile_tick+0xc0/0x100
[   33.397084]  ? __sanitizer_cov_trace_const_cmp4+0x24/0x80
[   33.397094]  ? riva_set_rop_solid+0x2a0/0x2a0
[   33.397102]  rivafb_set_par+0xbe/0x610
[   33.397111]  ? riva_set_rop_solid+0x2a0/0x2a0
[   33.397119]  fb_set_var+0x5bf/0xeb0
[   33.397127]  ? fb_blank+0x1a0/0x1a0
[   33.397134]  ? lock_acquire+0x1ef/0x530
[   33.397143]  ? lock_release+0x810/0x810
[   33.397151]  ? lock_is_held_type+0x100/0x140
[   33.397159]  ? ___might_sleep+0x1ee/0x2d0
[   33.397170]  ? __mutex_lock+0x620/0x1190
[   33.397180]  ? trace_hardirqs_on+0x6a/0x1c0
[   33.397190]  do_fb_ioctl+0x31e/0x700

Signed-off-by: Zheyu Ma <redacted>
---
 drivers/video/fbdev/riva/fbdev.c | 3 +++

2 more lines

diff --git a/drivers/video/fbdev/riva/fbdev.c b/drivers/video/fbdev/riva/fbdev.c
index 55554b0433cb..84d5e23ad7d3 100644
--- a/drivers/video/fbdev/riva/fbdev.c
+++ b/drivers/video/fbdev/riva/fbdev.c

@@ -1084,6 +1084,9 @@ static int rivafb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
 	int mode_valid = 0;
 	
 	NVTRACE_ENTER();
+	if (!var->pixclock)
+		return -EINVAL;
+
 	switch (var->bits_per_pixel) {
 	case 1 ... 8:
 		var->red.offset = var->green.offset = var->blue.offset = 0;

-- 
2.17.6

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 <redacted>
---
 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;

-- 
2.17.6