From: "Colin Walters" <walters@verbum.org>
To: "Christian Brauner" <brauner@kernel.org>
Cc: "Giuseppe Scrivano" <gscrivan@redhat.com>,
"Aleksa Sarai" <cyphar@cyphar.com>,
linux-kernel@vger.kernel.org, "Kees Cook" <keescook@chromium.org>,
bristot@redhat.com, "Eric W. Biederman" <ebiederm@xmission.com>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Alexander Larsson" <alexl@redhat.com>,
"Peter Zijlstra" <peterz@infradead.org>,
bmasney@redhat.com
Subject: Re: [PATCH v3 1/2] exec: add PR_HIDE_SELF_EXE prctl
Date: Sun, 29 Jan 2023 13:12:45 -0500 [thread overview]
Message-ID: <e637b476-6cc4-4d7f-bab2-4f623617a8ee@app.fastmail.com> (raw)
In-Reply-To: <20230129165812.sqypj6nzam7o33lf@wittgenstein>
On Sun, Jan 29, 2023, at 11:58 AM, Christian Brauner wrote:
> On Sun, Jan 29, 2023 at 08:59:32AM -0500, Colin Walters wrote:
>>
>>
>> On Wed, Jan 25, 2023, at 11:30 AM, Giuseppe Scrivano wrote:
>> >
>> > After reading some comments on the LWN.net article, I wonder if
>> > PR_HIDE_SELF_EXE should apply to CAP_SYS_ADMIN in the initial user
>> > namespace or if in this case root should keep the privilege to inspect
>> > the binary of a process. If a container runs with that many privileges
>> > then it has already other ways to damage the host anyway.
>>
>> Right, that's what I was trying to express with the "make it work the same as map_files". Hiding the entry entirely even for initial-namespace-root (real root) seems like it's going to potentially confuse profiling/tracing/debugging tools for no good reason.
>
> If this can be circumvented via CAP_SYS_ADMIN
To be clear, I'm proposing CAP_SYS_ADMIN in the current user namespace at the time of the prctl(). (Or if keeping around a reference just for this is too problematic, perhaps hardcoding to the init ns)
A process with CAP_SYS_ADMIN in a child namespace would still not be able to read the binary.
> then this mitigation
> becomes immediately way less interesting because the userspace
> mitigation we came up with protects against CAP_SYS_ADMIN as well
> without any regression risk.
The userspace mitigation here being "clone self to memfd"? But that's a sufficiently ugly workaround that it's created new problems; see https://lwn.net/Articles/918106/
next prev parent reply other threads:[~2023-01-29 18:13 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-20 10:25 [PATCH v3 1/2] exec: add PR_HIDE_SELF_EXE prctl Giuseppe Scrivano
2023-01-20 10:25 ` [PATCH v3 2/2] selftests: add tests for prctl(SET_HIDE_SELF_EXE) Giuseppe Scrivano
2023-01-20 16:05 ` Brian Masney
2023-01-23 18:41 ` [PATCH v3 1/2] exec: add PR_HIDE_SELF_EXE prctl Colin Walters
2023-01-23 19:21 ` Giuseppe Scrivano
2023-01-23 22:07 ` Colin Walters
2023-01-23 22:54 ` Giuseppe Scrivano
2023-01-23 23:14 ` Colin Walters
2023-01-24 1:53 ` Aleksa Sarai
2023-01-24 7:29 ` Giuseppe Scrivano
2023-01-25 15:28 ` Aleksa Sarai
2023-01-25 16:30 ` Giuseppe Scrivano
2023-01-29 13:59 ` Colin Walters
2023-01-29 16:58 ` Christian Brauner
2023-01-29 18:12 ` Colin Walters [this message]
2023-01-30 9:53 ` Christian Brauner
2023-01-30 10:06 ` Christian Brauner
2023-01-30 21:52 ` Colin Walters
2023-01-31 14:17 ` Giuseppe Scrivano
2023-02-25 0:27 ` Andrei Vagin
2023-02-28 14:19 ` Giuseppe Scrivano
2023-01-26 8:25 ` Christian Brauner
2023-01-24 19:17 ` Andrei Vagin
2023-01-27 12:31 ` Christian Brauner
2023-01-27 20:34 ` Kees Cook
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