[PATCH AUTOSEL 5.10 048/176] video: fbdev: riva: Error out if 'pixclock' equals zero

[Sasha Levin]

From: Zheyu Ma <zheyuma97@xxxxxxxxx>

[ Upstream commit f92763cb0feba247e0939ed137b495601fd072a5 ]

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 <zheyuma97@xxxxxxxxx>
Signed-off-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/1627293835-17441-4-git-send-email-zheyuma97@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/video/fbdev/riva/fbdev.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/video/fbdev/riva/fbdev.c b/drivers/video/fbdev/riva/fbdev.c
index ce55b9d2e862..7dd621c7afe4 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;
-- 
2.30.2