From: Jann Horn <jannh@google.com>
To: Kees Cook <kees@kernel.org>
Cc: Mateusz Guzik <mjguzik@gmail.com>,
Kees Cook <keescook@chromium.org>,
Christian Brauner <brauner@kernel.org>,
Eric Biederman <ebiederm@xmission.com>,
Jorge Merlino <jorge.merlino@canonical.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Thomas Gleixner <tglx@linutronix.de>,
Andy Lutomirski <luto@kernel.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
John Johansen <john.johansen@canonical.com>,
Paul Moore <paul@paul-moore.com>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
Stephen Smalley <stephen.smalley.work@gmail.com>,
Eric Paris <eparis@parisplace.org>,
Richard Haines <richard_c_haines@btinternet.com>,
Casey Schaufler <casey@schaufler-ca.com>,
Xin Long <lucien.xin@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
Todd Kjos <tkjos@google.com>,
Ondrej Mosnacek <omosnace@redhat.com>,
Prashanth Prahlad <pprahlad@redhat.com>,
Micah Morton <mortonm@chromium.org>,
Fenghua Yu <fenghua.yu@intel.com>,
Andrei Vagin <avagin@gmail.com>,
linux-kernel@vger.kernel.org, apparmor@lists.ubuntu.com,
linux-security-module@vger.kernel.org, selinux@vger.kernel.org,
linux-hardening@vger.kernel.org, oleg@redhat.com
Subject: Re: [PATCH 1/2] fs/exec: Explicitly unshare fs_struct on exec
Date: Tue, 13 May 2025 23:09:48 +0200 [thread overview]
Message-ID: <CAG48ez0aP8LaGppy6Yon7xcFbQa1=CM-HXSZChvXYV2VJZ8y7g@mail.gmail.com> (raw)
In-Reply-To: <D03AE210-6874-43B6-B917-80CD259AE2AC@kernel.org>
On Tue, May 13, 2025 at 10:57 PM Kees Cook <kees@kernel.org> wrote:
> On May 13, 2025 6:05:45 AM PDT, Mateusz Guzik <mjguzik@gmail.com> wrote:
> >Here is my proposal: *deny* exec of suid/sgid binaries if fs_struct is
> >shared. This will have to be checked for after the execing proc becomes
> >single-threaded ofc.
>
> Unfortunately the above Chrome helper is setuid and uses CLONE_FS.
Chrome first launches a setuid helper, and then the setuid helper does
CLONE_FS. Mateusz's proposal would not impact this usecase.
Mateusz is proposing to block the case where a process first does
CLONE_FS, and *then* one of the processes sharing the fs_struct does a
setuid execve(). Linux already downgrades such an execve() to be
non-setuid, which probably means anyone trying to do this will get
hard-to-understand problems. Mateusz' proposal would just turn this
hard-to-debug edgecase, which already doesn't really work, into a
clean error; I think that is a nice improvement even just from the
UAPI standpoint.
If this change makes it possible to clean up the kernel code a bit, even better.
next prev parent reply other threads:[~2025-05-13 21:10 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-06 8:27 [PATCH 0/2] " Kees Cook
2022-10-06 8:27 ` [PATCH 1/2] " Kees Cook
2022-10-06 9:05 ` Christian Brauner
2022-10-06 10:48 ` David Laight
2022-10-06 14:13 ` Jann Horn
2022-10-06 15:25 ` Kees Cook
2022-10-06 15:35 ` Jann Horn
2025-05-13 13:05 ` Mateusz Guzik
2025-05-13 15:29 ` Eric W. Biederman
2025-05-13 20:57 ` Kees Cook
2025-05-13 21:09 ` Jann Horn [this message]
2025-05-13 22:16 ` Eric W. Biederman
2025-05-14 0:03 ` Mateusz Guzik
2025-05-14 15:33 ` Eric W. Biederman
2025-05-14 15:42 ` Kees Cook
2025-05-15 16:48 ` Eric W. Biederman
2025-05-13 23:15 ` Kees Cook
2022-10-14 3:18 ` Andy Lutomirski
2022-10-14 3:54 ` Kees Cook
2022-10-14 15:35 ` Jann Horn
2022-10-18 7:09 ` Kees Cook
2022-10-18 11:19 ` Jann Horn
2022-10-14 22:03 ` David Laight
2022-11-28 17:49 ` Eric W. Biederman
2022-10-06 8:27 ` [PATCH 2/2] exec: Remove LSM_UNSAFE_SHARE Kees Cook
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