[PATCH] fbdev: pm3fb: Fix potential divide by zero

[Alex Guo <alexguo1023@gmail.com>]

variable var->pixclock can be set by user. In case it equals to
 zero, divide by zero would occur in pm3fb_check_var. Similar
crashes have happened in other fbdev drivers. There is no check
and modification on var->pixclock along the call chain to
pm3fb_check_var. So we fix this by checking whether 'pixclock'
is zero.

Similar commit: commit 16844e58704 ("video: fbdev: tridentfb:
Error out if 'pixclock' equals zero")

Signed-off-by: Alex Guo <alexguo1023@gmail.com>
---
 drivers/video/fbdev/pm3fb.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/video/fbdev/pm3fb.c b/drivers/video/fbdev/pm3fb.c
index 6e55e42514d6..d9b3f1937ce6 100644
--- a/drivers/video/fbdev/pm3fb.c
+++ b/drivers/video/fbdev/pm3fb.c
@@ -998,6 +998,9 @@ static int pm3fb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
 		return -EINVAL;
 	}
 
+	if (!var->pixclock)
+		return -EINVAL;
+		
 	if (PICOS2KHZ(var->pixclock) > PM3_MAX_PIXCLOCK) {
 		DPRINTK("pixclock too high (%ldKHz)\n",
 			PICOS2KHZ(var->pixclock));
-- 
2.34.1