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From:   Zheyu Ma <zheyuma97@gmail.com>
To:     deller@gmx.de
Cc:     linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, Zheyu Ma <zheyuma97@gmail.com>
Subject: [PATCH 2/7] video: fbdev: neofb: Fix the check of 'var->pixclock'
Date:   Mon,  4 Apr 2022 16:47:18 +0800
Message-Id: <20220404084723.79089-3-zheyuma97@gmail.com>
In-Reply-To: <20220404084723.79089-1-zheyuma97@gmail.com>
References: <20220404084723.79089-1-zheyuma97@gmail.com>
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The previous check against 'var->pixclock' doesn't return -EINVAL when
it equals zero, but the driver uses it again, causing the divide error.

Fix this by returning when 'var->pixclock' is zero.

The following log reveals it:

[   49.704574] divide error: 0000 [#1] PREEMPT SMP KASAN PTI
[   49.704593] RIP: 0010:neofb_set_par+0x190f/0x49a0
[   49.704635] Call Trace:
[   49.704636]  <TASK>
[   49.704650]  fb_set_var+0x604/0xeb0
[   49.704702]  do_fb_ioctl+0x234/0x670
[   49.704745]  fb_ioctl+0xdd/0x130
[   49.704753]  do_syscall_64+0x3b/0x90

Signed-off-by: Zheyu Ma <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 966df2a07360..28d32cbf496b 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 (var->pixclock && PICOS2KHZ(var->pixclock) > par->maxClock)
+	if (!var->pixclock || PICOS2KHZ(var->pixclock) > par->maxClock)
 		return -EINVAL;
 
 	/* Is the mode larger than the LCD panel? */
-- 
2.25.1