[PATCH v15 bpf-next 3/6] Documentation/bpf: Add documentation for filesystem kfuncs
From: Song Liu <song@kernel.org>
Date: 2023-11-29 23:44:46
Also in:
bpf, linux-fsdevel
Subsystem:
bpf [general] (safe dynamic programs and tools), documentation, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Jonathan Corbet, Linus Torvalds
Add a brief introduction for file system kfuncs: bpf_get_file_xattr() bpf_get_fsverity_digest() The documentation highlights the strategy to avoid recursions of these kfuncs. Signed-off-by: Song Liu <song@kernel.org> --- Documentation/bpf/fs_kfuncs.rst | 21 +++++++++++++++++++++ Documentation/bpf/index.rst | 1 + 2 files changed, 22 insertions(+) create mode 100644 Documentation/bpf/fs_kfuncs.rst
diff --git a/Documentation/bpf/fs_kfuncs.rst b/Documentation/bpf/fs_kfuncs.rst
new file mode 100644
index 000000000000..8762c3233a3d
--- /dev/null
+++ b/Documentation/bpf/fs_kfuncs.rst@@ -0,0 +1,21 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _fs_kfuncs-header-label: + +===================== +BPF filesystem kfuncs +===================== + +BPF LSM programs need to access filesystem data from LSM hooks. The following +BPF kfuncs can be used to get these data. + + * ``bpf_get_file_xattr()`` + + * ``bpf_get_fsverity_digest()`` + +To avoid recursions, these kfuncs follow the following rules: + +1. These kfuncs are only permitted from BPF LSM function. +2. These kfuncs should not call into other LSM hooks, i.e. security_*(). For + example, ``bpf_get_file_xattr()`` does not use ``vfs_getxattr()``, because + the latter calls LSM hook ``security_inode_getxattr``.
diff --git a/Documentation/bpf/index.rst b/Documentation/bpf/index.rst
index aeaeb35e6d4a..0bb5cb8157f1 100644
--- a/Documentation/bpf/index.rst
+++ b/Documentation/bpf/index.rst@@ -21,6 +21,7 @@ that goes into great technical depth about the BPF Architecture. helpers kfuncs cpumasks + fs_kfuncs programs maps bpf_prog_run
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2.34.1