linux-kernel - Re: [REVIEW][PATCH 2/3] exec: Don't allow ptracing an exec of an unreadable file

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Date:   Thu, 17 Nov 2016 22:32:59 +0100
From:   Willy Tarreau <w@....eu>
To:     Kees Cook <keescook@...omium.org>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Michal Hocko <mhocko@...nel.org>, Jann Horn <jann@...jh.net>,
        Andy Lutomirski <luto@...capital.net>
Subject: Re: [REVIEW][PATCH 2/3] exec: Don't allow ptracing an exec of an
 unreadable file

On Thu, Nov 17, 2016 at 01:07:33PM -0800, Kees Cook wrote:
> I'm not opposed to a sysctl for this. Regardless, I think we need to
> embrace this idea now, though, since we'll soon end up with
> architectures that enforce executable-only memory, in which case
> ptrace will again fail. Almost better to get started here and then not
> have more surprises later.

Also that makes me realize that by far the largest use case of ptrace
is strace and that strace needs very little capabilities. I guess that
most users would be fine with having only pointers and not contents
for addresses or read/write of data, as they have on some other OSes,
when the process is not readable. But in my opinion when a process
is executable we should be able to trace its execution (even without
memory read access).

Willy