[PATCH bpf-next 0/4] Introduce bpf_kernfs_read_xattr

[Song Liu]

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