linux-kernel - [PATCH 0/2] Revert "fs/exec: allow to unshare a time namespace on vfork+exec"

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Message-ID: <20220913102551.1121611-1-avagin@google.com>
Date:   Tue, 13 Sep 2022 03:25:49 -0700
From:   Andrei Vagin <avagin@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org, Andrei Vagin <avagin@...gle.com>
Subject: [PATCH 0/2] Revert "fs/exec: allow to unshare a time namespace on vfork+exec"

This reverts commits:
133e2d3e81de ("fs/exec: allow to unshare a time namespace on vfork+exec")
6342140db660 ("selftests/timens: add a test for vfork+exit")

Alexey pointed out a few undesirable side effects of the reverted change.
First, it doesn't take into account that CLONE_VFORK can be used with
CLONE_THREAD. Second, a child process doesn't enter a target time name-space,
if its parent dies before the child calls exec. It happens because the parent
clears vfork_done.

Eric W. Biederman suggests installing a time namespace as a task gets a new mm.
It includes all new processes cloned without CLONE_VM and all tasks that call
exec(). This is an user API change, but we think there aren't users that depend
on the old behavior.

It is too late to make such changes in this release, so let's roll back
this patch and introduce the right one in the next release.

Andrei Vagin (2):
  Revert "selftests/timens: add a test for vfork+exit"
  Revert "fs/exec: allow to unshare a time namespace on vfork+exec"

 fs/exec.c                                   |  7 --
 kernel/fork.c                               |  5 +-
 kernel/nsproxy.c                            |  3 +-
 tools/testing/selftests/timens/Makefile     |  2 +-
 tools/testing/selftests/timens/vfork_exec.c | 90 ---------------------
 5 files changed, 3 insertions(+), 104 deletions(-)
 delete mode 100644 tools/testing/selftests/timens/vfork_exec.c

-- 
2.37.2.789.g6183377224-goog