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Message-Id: <20250912-work-namespace-v2-0-1a247645cef5@kernel.org>
Date: Fri, 12 Sep 2025 13:52:23 +0200
From: Christian Brauner <brauner@...nel.org>
To: Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>,
linux-fsdevel@...r.kernel.org
Cc: Josef Bacik <josef@...icpanda.com>, Jeff Layton <jlayton@...nel.org>,
Mike Yuan <me@...dnzj.com>,
Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>,
Lennart Poettering <mzxreary@...inter.de>,
Daan De Meyer <daan.j.demeyer@...il.com>, Aleksa Sarai <cyphar@...har.com>,
Alexander Viro <viro@...iv.linux.org.uk>, Jens Axboe <axboe@...nel.dk>,
Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>,
Michal Koutný <mkoutny@...e.com>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
Chuck Lever <chuck.lever@...cle.com>, linux-nfs@...r.kernel.org,
linux-kselftest@...r.kernel.org, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
netdev@...r.kernel.org, Christian Brauner <brauner@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v2 00/33] ns: support file handles
For a while now we have supported file handles for pidfds. This has
proven to be very useful.
Extend the concept to cover namespaces as well. After this patchset it
is possible to encode and decode namespace file handles using the
commong name_to_handle_at() and open_by_handle_at() apis.
Namespaces file descriptors can already be derived from pidfds which
means they aren't subject to overmount protection bugs. IOW, it's
irrelevant if the caller would not have access to an appropriate
/proc/<pid>/ns/ directory as they could always just derive the namespace
based on a pidfd already.
It has the same advantage as pidfds. It's possible to reliably and for
the lifetime of the system refer to a namespace without pinning any
resources and to compare them.
Permission checking is kept simple. If the caller is located in the
namespace the file handle refers to they are able to open it otherwise
they must hold privilege over the owning namespace of the relevant
namespace.
Both the network namespace and the mount namespace already have an
associated cookie that isn't recycled and is fully exposed to userspace.
Move this into ns_common and use the same id space for all namespaces so
they can trivially and reliably be compared.
There's more coming based on the iterator infrastructure but the series
is large enough and focuses on file handles.
Extensive selftests included.
Signed-off-by: Christian Brauner <brauner@...nel.org>
---
Changes in v2:
- Address various review comments.
- Use a common NS_GET_ID ioctl() instead of individual ioctls.
- Link to v1: https://lore.kernel.org/20250910-work-namespace-v1-0-4dd56e7359d8@kernel.org
---
Christian Brauner (33):
pidfs: validate extensible ioctls
nsfs: drop tautological ioctl() check
nsfs: validate extensible ioctls
block: use extensible_ioctl_valid()
ns: move to_ns_common() to ns_common.h
nsfs: add nsfs.h header
ns: uniformly initialize ns_common
cgroup: use ns_common_init()
ipc: use ns_common_init()
mnt: use ns_common_init()
net: use ns_common_init()
pid: use ns_common_init()
time: use ns_common_init()
user: use ns_common_init()
uts: use ns_common_init()
ns: remove ns_alloc_inum()
nstree: make iterator generic
mnt: support ns lookup
cgroup: support ns lookup
ipc: support ns lookup
net: support ns lookup
pid: support ns lookup
time: support ns lookup
user: support ns lookup
uts: support ns lookup
ns: add to_<type>_ns() to respective headers
nsfs: add current_in_namespace()
nsfs: support file handles
nsfs: support exhaustive file handles
nsfs: add missing id retrieval support
tools: update nsfs.h uapi header
selftests/namespaces: add identifier selftests
selftests/namespaces: add file handle selftests
block/blk-integrity.c | 8 +-
fs/fhandle.c | 6 +
fs/internal.h | 1 +
fs/mount.h | 10 +-
fs/namespace.c | 156 +--
fs/nsfs.c | 201 ++-
fs/pidfs.c | 2 +-
include/linux/cgroup.h | 5 +
include/linux/exportfs.h | 6 +
include/linux/fs.h | 14 +
include/linux/ipc_namespace.h | 5 +
include/linux/ns_common.h | 29 +
include/linux/nsfs.h | 40 +
include/linux/nsproxy.h | 11 -
include/linux/nstree.h | 89 ++
include/linux/pid_namespace.h | 5 +
include/linux/proc_ns.h | 32 +-
include/linux/time_namespace.h | 9 +
include/linux/user_namespace.h | 5 +
include/linux/utsname.h | 5 +
include/net/net_namespace.h | 6 +
include/uapi/linux/fcntl.h | 1 +
include/uapi/linux/nsfs.h | 15 +-
init/main.c | 2 +
ipc/msgutil.c | 1 +
ipc/namespace.c | 12 +-
ipc/shm.c | 2 +
kernel/Makefile | 2 +-
kernel/cgroup/cgroup.c | 2 +
kernel/cgroup/namespace.c | 24 +-
kernel/nstree.c | 233 ++++
kernel/pid_namespace.c | 13 +-
kernel/time/namespace.c | 23 +-
kernel/user_namespace.c | 17 +-
kernel/utsname.c | 28 +-
net/core/net_namespace.c | 59 +-
tools/include/uapi/linux/nsfs.h | 17 +-
tools/testing/selftests/namespaces/.gitignore | 2 +
tools/testing/selftests/namespaces/Makefile | 7 +
tools/testing/selftests/namespaces/config | 7 +
.../selftests/namespaces/file_handle_test.c | 1429 ++++++++++++++++++++
tools/testing/selftests/namespaces/nsid_test.c | 986 ++++++++++++++
42 files changed, 3257 insertions(+), 270 deletions(-)
---
base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
change-id: 20250905-work-namespace-c68826dda0d4
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