linux-kernel - Re: [PATCH v3 1/2] exec: add PR_HIDE_SELF

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Message-Id: <167482213665.546991.3626486119597692007.b4-ty@kernel.org>
Date:   Fri, 27 Jan 2023 13:31:13 +0100
From:   Christian Brauner <brauner@...nel.org>
To:     Giuseppe Scrivano <gscrivan@...hat.com>
Cc:     Christian Brauner <brauner@...nel.org>, keescook@...omium.org,
        bristot@...hat.com, ebiederm@...ssion.com, cyphar@...har.com,
        viro@...iv.linux.org.uk, alexl@...hat.com, peterz@...radead.org,
        bmasney@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] exec: add PR_HIDE_SELF_EXE prctl

From: Christian Brauner (Microsoft) <brauner@...nel.org>


On Fri, 20 Jan 2023 11:25:11 +0100, 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.
> 
> This is useful for preventing issues like CVE-2019-5736, where an
> attacker can gain host root access by overwriting the binary
> in OCI runtimes through file-descriptor mishandling in containers.
> 
> [...]

Only needed for privileged sandboxes. The userspace mitigations Aleksa
and I did for the CVE in all affected runtimes back then are nifty but
complicated. The patch is a decent compromise.
Picking up this prctl() for now,

[1/2] exec: add PR_HIDE_SELF_EXE prctl
      commit: 673301182d473ef61a98c292cf64650c73117172
[2/2] selftests: add tests for prctl(SET_HIDE_SELF_EXE)
      commit: bafa339eda3f79d567386e1fae59bb0537156c96