linux-kernel - [PATCH bpf-next 0/2] Add kfuncs to support reading xattr from dentry

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Message-ID: <20240725234706.655613-1-song@kernel.org>
Date: Thu, 25 Jul 2024 16:47:04 -0700
From: Song Liu <song@...nel.org>
To: bpf@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...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,
	Song Liu <song@...nel.org>
Subject: [PATCH bpf-next 0/2] Add kfuncs to support reading xattr from dentry

The use case is to tag directories with xattr. For example, "user.allow_x"
tag on /bin would allow execution of all files under /bin. To achieve this,
we start from the security_file_open() hook and read xattr of all the
parent directories.

4 kfuncs are added in this set:

  bpf_get_dentry_xattr
  bpf_file_dentry
  bpf_dget_parent
  bpf_dput

The first is used to read xattr from dentry; while the other 3 are used to
walk the directory tree.

Note that, these functions are only allowed from LSM hooks.

Song Liu (2):
  bpf: Add kfunc bpf_get_dentry_xattr() to read xattr from dentry
  selftests/bpf: Add tests for bpf_get_dentry_xattr

 kernel/trace/bpf_trace.c                      | 60 +++++++++++++++---
 .../selftests/bpf/prog_tests/fs_kfuncs.c      | 61 +++++++++++++++++--
 .../selftests/bpf/progs/test_dentry_xattr.c   | 46 ++++++++++++++
 .../selftests/bpf/progs/test_get_xattr.c      | 16 ++++-
 4 files changed, 168 insertions(+), 15 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/test_dentry_xattr.c

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2.43.0