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@ucr.edu
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