From:   Giuseppe Scrivano <gscrivan@redhat.com>
To:     "Colin Walters" <walters@verbum.org>
Cc:     linux-kernel@vger.kernel.org, "Kees Cook" <keescook@chromium.org>,
        bristot@redhat.com, "Eric W. Biederman" <ebiederm@xmission.com>,
        brauner@kernel.org, "Aleksa Sarai" <cyphar@cyphar.com>,
        "Al Viro" <viro@zeniv.linux.org.uk>,
        "Alexander Larsson" <alexl@redhat.com>, peterz@infradead.org,
        bmasney@redhat.com
Subject: Re: [PATCH v3 1/2] exec: add PR_HIDE_SELF_EXE prctl
References: <20230120102512.3195094-1-gscrivan@redhat.com>
        <db72efdd-5cb2-4578-a322-bf894fcf6066@app.fastmail.com>
Date:   Mon, 23 Jan 2023 20:21:28 +0100
In-Reply-To: <db72efdd-5cb2-4578-a322-bf894fcf6066@app.fastmail.com> (Colin
        Walters's message of "Mon, 23 Jan 2023 13:41:04 -0500")
Message-ID: <874jshdpl3.fsf@redhat.com>
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"Colin Walters" <walters@verbum.org> writes:

> On Fri, Jan 20, 2023, at 5:25 AM, Giuseppe Scrivano wrote:
>> This patch adds a new prctl called PR_HIDE_SELF_EXE which allows
>> processes to hide their own /proc/*/exe file. When this prctl is
>> used, every access to /proc/*/exe for the calling process will
>> fail with ENOENT.
>
> How about a mount option for procfs like `mount -t procfs procfs /proc -o rw,nosuid,nodev,magiclink-no-xdev`
>
> Where `magiclink-no-xdev` would cause all magic links to fail to cross a pid namespace or so?

wouldn't that break also stuff like "/proc/self/fd/$FD" after you join a
different PID namespace?