linux-kernel - Re: [PATCH] seccomp: Use -1 marker for end of mode 1 syscall list

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Message-ID: <CALCETrUfsRy+SmQi9FCYKR-Nvm0=NKHXtk+O-ozk962B5-7Yyw@mail.gmail.com>
Date:   Fri, 19 Jun 2020 12:54:26 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Arnd Bergmann <arnd@...db.de>, Will Drewry <wad@...omium.org>,
        "open list:MIPS" <linux-mips@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH] seccomp: Use -1 marker for end of mode 1 syscall list

On Fri, Jun 19, 2020 at 12:53 PM Kees Cook <keescook@...omium.org> wrote:
>
> On Fri, Jun 19, 2020 at 12:42:14PM -0700, Andy Lutomirski wrote:
> > On Fri, Jun 19, 2020 at 12:37 PM Kees Cook <keescook@...omium.org> wrote:
> > >
> > > The terminator for the mode 1 syscalls list was a 0, but that could be
> > > a valid syscall number (e.g. x86_64 __NR_read). By luck, __NR_read was
> > > listed first and the loop construct would not test it, so there was no
> > > bug. However, this is fragile. Replace the terminator with -1 instead,
> > > and make the variable name for mode 1 syscall lists more descriptive.
> >
> > Could the architecture instead supply the length of the list?
>
> It could, but I didn't like the way the plumbing for that looked.

Fair enough.

>
> --
> Kees Cook