On 2/2/22 15:33, Yizhuo Zhai wrote:
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. Fix this by adding the check before the function
call.
Signed-off-by: Yizhuo Zhai <yzhai003@xxxxxxx>
---
drivers/video/fbdev/core/fbmem.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 0fa7ede94fa6..d5dec24c4d16 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1162,6 +1162,11 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
case FBIOBLANK:
console_lock();
lock_fb_info(info);
+ if (arg > FB_BLANK_POWERDOWN) {
+ unlock_fb_info(info);
+ console_unlock();
+ return -EINVAL;
+ }
Is it really necessary to perform this check within the lock ?
arg is a passed in value, and FB_BLANK_POWERDOWN.
It seems to me that
case FBIOBLANK:
if (arg > FB_BLANK_POWERDOWN)
return -EINVAL;
console_lock();
...
should be sufficient.
Sorry if I missed some previous discussion; this is the first time
I looked at this patch.
Guenter
