Messages in this thread | | | Date | Wed, 2 Feb 2022 15:45:27 -0800 | Subject | Re: [PATCH v5] fbdev: fbmem: Fix the implicit type casting | From | Guenter Roeck <> |
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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
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