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[v4,bpf-next,6/9] Documentation/bpf: Add documentation for filesystem kfuncs

Message ID 20231023224100.2573116-7-song@kernel.org (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: File verification with LSM and fsverity | expand

Checks

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bpf/vmtest-bpf-next-PR fail PR summary
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 9 this patch: 9
netdev/cc_maintainers warning 9 maintainers not CCed: linux-doc@vger.kernel.org corbet@lwn.net yonghong.song@linux.dev jolsa@kernel.org kpsingh@kernel.org john.fastabend@gmail.com sdf@google.com haoluo@google.com martin.lau@linux.dev
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Commit Message

Song Liu Oct. 23, 2023, 10:40 p.m. UTC
Add a brief introduction for file system 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 mbox series

Patch

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