From patchwork Wed Nov 29 23:44:14 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Liu X-Patchwork-Id: 13473662 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2A8804CB33; Wed, 29 Nov 2023 23:44:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="J63N/GQF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B3B19C433C7; Wed, 29 Nov 2023 23:44:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1701301486; bh=Xm4N+IK6cCfxBp62n/HaElU5RuamPewSwlV6BouTrZQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=J63N/GQFKDG5x4jb2xPuNwBbkihTR5rxTb/mLLJ+2+o5l6ncGvIk22gAwgOTXBxCu mlAij7sPeR4bG1XZwq5u4GH6uASRXbpDafxAgA78mJLus9EqgaKU4jdOAn6hwQQAgi qOyhcRy15ZZfNX9+GBItKWJqR3Kb6toIxNKIdHphQKCSNUbLc/zspLqQs8PZH71mN4 lVwa0fBhZdBhyOCPCMMQrjtMu1xTPrvYYwJPzvaUsoMw6IG0QaWiGc6dHQV7PevFEL DKrojkppxksTghCUmDyaWN86YyyIOxW7O/W9Ed0KNHzVe80FS6PF7mBMR8cyAmCT8V lUHei9A549osg== From: Song Liu To: bpf@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org, fsverity@lists.linux.dev Cc: ebiggers@kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, brauner@kernel.org, viro@zeniv.linux.org.uk, casey@schaufler-ca.com, amir73il@gmail.com, kpsingh@kernel.org, roberto.sassu@huawei.com, kernel-team@meta.com, Song Liu Subject: [PATCH v15 bpf-next 3/6] Documentation/bpf: Add documentation for filesystem kfuncs Date: Wed, 29 Nov 2023 15:44:14 -0800 Message-Id: <20231129234417.856536-4-song@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231129234417.856536-1-song@kernel.org> References: <20231129234417.856536-1-song@kernel.org> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 --- 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