linux-kernel - [PATCH bpf-next 0/4] Introduce bpf_kernfs_read

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Message-ID: <20250618233739.189106-1-song@kernel.org>
Date: Wed, 18 Jun 2025 16:37:35 -0700
From: Song Liu <song@...nel.org>
To: bpf@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org
Cc: kernel-team@...a.com,
	andrii@...nel.org,
	eddyz87@...il.com,
	ast@...nel.org,
	daniel@...earbox.net,
	martin.lau@...ux.dev,
	viro@...iv.linux.org.uk,
	brauner@...nel.org,
	jack@...e.cz,
	kpsingh@...nel.org,
	mattbobrowski@...gle.com,
	amir73il@...il.com,
	gregkh@...uxfoundation.org,
	tj@...nel.org,
	daan.j.demeyer@...il.com,
	Song Liu <song@...nel.org>
Subject: [PATCH bpf-next 0/4] Introduce bpf_kernfs_read_xattr

Introduce a new kfunc bpf_kernfs_read_xattr, which can read xattr from
kernfs nodes (cgroupfs, for example). The primary users are LSMs, for
example, from systemd. sched_ext could also use xattrs on cgroupfs nodes.
However, this is not allowed yet, because bpf_kernfs_read_xattr is only
allowed from LSM hooks. The plan is to address sched_ext later (or in a
later revision of this set).

Song Liu (4):
  kernfs: Add __kernfs_xattr_get for RCU protected access
  bpf: Introduce bpf_kernfs_read_xattr to read xattr of kernfs nodes
  bpf: Mark cgroup_subsys_state->cgroup RCU safe
  selftests/bpf: Add tests for bpf_kernfs_read_xattr

 fs/bpf_fs_kfuncs.c                            |  33 ++++
 fs/kernfs/inode.c                             |  14 ++
 include/linux/kernfs.h                        |   2 +
 kernel/bpf/verifier.c                         |   5 +
 .../selftests/bpf/prog_tests/kernfs_xattr.c   | 145 ++++++++++++++++++
 .../selftests/bpf/progs/kernfs_read_xattr.c   | 117 ++++++++++++++
 .../selftests/bpf/progs/read_cgroupfs_xattr.c |  60 ++++++++
 7 files changed, 376 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/kernfs_xattr.c
 create mode 100644 tools/testing/selftests/bpf/progs/kernfs_read_xattr.c
 create mode 100644 tools/testing/selftests/bpf/progs/read_cgroupfs_xattr.c

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2.47.1