Re: [PATCH v4] tools/x86: Add a kcpuid tool to show raw CPU features

From: Feng Tang
Date: Tue Jan 19 2021 - 08:11:24 EST


On Tue, Jan 19, 2021 at 10:11:16AM +0100, Borislav Petkov wrote:
> On Tue, Jan 19, 2021 at 01:19:42PM +0800, Feng Tang wrote:
> > Sorry, after testing on more platforms, the following is needed to fix
> > a potential array overflow ((a full patch with fix is also attached)
> >
> > diff --git a/tools/arch/x86/kcpuid/kcpuid.c b/tools/arch/x86/kcpuid/kcpuid.c
> > index 3ea607b..bf68335 100644
> > --- a/tools/arch/x86/kcpuid/kcpuid.c
> > +++ b/tools/arch/x86/kcpuid/kcpuid.c
> > @@ -329,7 +329,8 @@ static int parse_line(char *line)
> > range = leafs_basic;
> >
> > index &= 0x7FFFFFFF;
> > - if ((int)index > range->nr)
> > + /* range->nr equals to max index plus 1 */
> > + if ((int)index >= range->nr)
>
> That comment is basically repeating the code. What it should do is
> explain *why* that test is being done or not be there at all.

Right! So this is better?
/* Skip line parsing for non-existing indexes */

Thanks,
Feng

> --
> Regards/Gruss,
> Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette