linux-kernel - Re: [PATCH 09/12] x86/process: Pin the target stack in get

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Message-ID: <20160926051053.GA6713@hopstrocity>
Date:   Sun, 25 Sep 2016 23:10:53 -0600
From:   Tycho Andersen <tycho.andersen@...onical.com>
To:     Jann Horn <jann@...jh.net>
Cc:     Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...capital.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>
Subject: Re: [PATCH 09/12] x86/process: Pin the target stack in get_wchan()

On Fri, Sep 23, 2016 at 08:34:43PM +0200, Jann Horn wrote:
> On Fri, Sep 23, 2016 at 11:28:26AM -0700, Kees Cook wrote:
> > Does CRIU use this? I wouldn't expect so, since they're using ptrace,
> > IIUC, to freeze/restore.
> 
> As far as I can tell:
> 
> parse_pid_stat() parses them into a struct proc_pid_stat as "esp" and "eip",
> but those struct members are never used (like, probably, most other members
> of that struct).

Yes, that's my reading of it too.

> child_opened_proc.c just opens /proc/%d/stat and then closes it again
> immediately.

This is just a test for ordering of things that are restored, and it
could use any file in /proc, stat was just convenient.

> So in summary: I don't think so.

Yep, agreed.

Tycho