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

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Date:   Sun, 17 Feb 2019 09:30:17 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Samuel Dionne-Riel <samuel@...nne-riel.com>,
        Richard Weinberger <richard.weinberger@...il.com>,
        Graham Christensen <graham@...hamc.com>,
        Michal Hocko <mhocko@...e.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] exec: load_script: Do not exec truncated interpreter path

On Sun, Feb 17, 2019 at 1:09 AM Kees Cook <keescook@...omium.org> 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?

                   Linus