In function do_fb_ioctl(), the "arg" is the type of unsigned long,
and in "case FBIOBLANK:" this argument is casted into an int before
passig to fb_blank(). In fb_blank(), the comparision
if (blank > FB_BLANK_POWERDOWN) would be bypass if the original
"arg" is a large number, which is possible because it comes from
the user input.

Signed-off-by: Yizhuo Zhai <yzhai003@ucr.edu>
---
 drivers/video/fbdev/core/fbmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 0fa7ede94fa6..a5f71c191122 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1064,7 +1064,7 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
 EXPORT_SYMBOL(fb_set_var);
 
 int
-fb_blank(struct fb_info *info, int blank)
+fb_blank(struct fb_info *info, unsigned long blank)
 {
 	struct fb_event event;
 	int ret = -EINVAL;
-- 
2.25.1