Re: [PATCH v4] exec: load_script: Do not exec truncated interpreter path

[Kees Cook]

On Sun, Feb 17, 2019 at 9:30 AM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Sun, Feb 17, 2019 at 1:09 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> >
> > +static inline char *next_spacetab(char *first, const char *last)
> > +{
> > +       for (; first <= last; first++)
> > +               if (spacetab(*first))
> > +                       return first;
> > +       return NULL;
> > +}
>
> I think this should be "next_terminator()" and also stop at NUL.
>
> You do check for the NUL case here:
>
> > +               if (!next_spacetab(cp, buf_end) && *buf_end)
> > +                       return -ENOEXEC;
>
> but it means that if there's no space ot tab and it's a short file,
> you pointlessly walk to the end. No?

Yeah, that works. I'll send v5.

-- 
Kees Cook