From patchwork Mon Oct 23 16:03:44 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Liu X-Patchwork-Id: 13433103 X-Patchwork-Delegate: bpf@iogearbox.net 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 B7A7F1C28A; Mon, 23 Oct 2023 16:04:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="tjk1iogi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9A0FCC433C7; Mon, 23 Oct 2023 16:04:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1698077052; bh=KegfHtw+dipb9WMoL0tp2jttgRiQoKqpiiVcpl1j3Jg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tjk1iogiNLEaW7wZOztpkfWU38o7Ia5y5RF3HOSi7gfjYRP8zjIt2jdNZ4rziDKnY QFmouIlGJgYgSiXhVvrZ6zYdF8kRD+HvlOwu5twiXkq1iamtbPfs2rNswJSHi2ADpq aE8Dh7WMlgO4BB1ve+ndY1In7LQ0Ux0p9dvQIDdSd76xnDssne6BPlU3KKt1YIsjTv 4RkCjm+y1D3UgH1yytvJGTrJQgZFcR+kD06NbAP6qfTM6IZaztwqHQiPbSWtLL05oB sgy8Wqai7c6hccqW8KNdBm3J0t68t73ZMBdBjAN2kMpJcDijAGO9BRqMv8Wsl9i8e+ 8N1nzxph+9L1w== From: Song Liu To: bpf@vger.kernel.org, fsverity@lists.linux.dev Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, kernel-team@meta.com, ebiggers@kernel.org, tytso@mit.edu, roberto.sassu@huaweicloud.com, Song Liu Subject: [PATCH v3 bpf-next 4/9] bpf: Add kfunc bpf_get_file_xattr Date: Mon, 23 Oct 2023 09:03:44 -0700 Message-Id: <20231023160349.4161154-5-song@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231023160349.4161154-1-song@kernel.org> References: <20231023160349.4161154-1-song@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net This kfunc can be used to read xattr of a file. To avoid recursion, only allow calling this kfunc from LSM hooks. Signed-off-by: Song Liu --- kernel/trace/bpf_trace.c | 56 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 43ed45a83ee2..4178d0e339d3 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -24,6 +24,7 @@ #include #include #include +#include #include @@ -1436,6 +1437,61 @@ static int __init bpf_key_sig_kfuncs_init(void) late_initcall(bpf_key_sig_kfuncs_init); #endif /* CONFIG_KEYS */ +/* filesystem kfuncs */ +__diag_push(); +__diag_ignore_all("-Wmissing-prototypes", + "kfuncs which will be used in BPF programs"); + +/** + * bpf_get_file_xattr - get xattr of a file + * @file: file to get xattr from + * @name__const_str: name of the xattr + * @value_ptr: output buffer of the xattr value + * + * Get xattr *name__const_str* of *file* and store the output in *value_ptr*. + * + * Return: 0 on success, a negative value on error. + */ +__bpf_kfunc int bpf_get_file_xattr(struct file *file, const char *name__const_str, + struct bpf_dynptr_kern *value_ptr) +{ + struct dentry *dentry; + void *value; + + value = bpf_dynptr_slice_rdwr(value_ptr, 0, NULL, 0); + if (IS_ERR_OR_NULL(value)) + return PTR_ERR(value); + + dentry = file_dentry(file); + return __vfs_getxattr(dentry, dentry->d_inode, name__const_str, + value, __bpf_dynptr_size(value_ptr)); +} + +__diag_pop(); + +static int bpf_get_file_xattr_filter(const struct bpf_prog *prog, u32 kfunc_id) +{ + /* Only allow to attach from LSM hooks, to avoid recursion */ + return prog->type != BPF_PROG_TYPE_LSM ? -EACCES : 0; +} + +BTF_SET8_START(fs_kfunc_set) +BTF_ID_FLAGS(func, bpf_get_file_xattr, KF_SLEEPABLE) +BTF_SET8_END(fs_kfunc_set) + +const struct btf_kfunc_id_set bpf_fs_kfunc_set = { + .owner = THIS_MODULE, + .set = &fs_kfunc_set, + .filter = bpf_get_file_xattr_filter, +}; + +static int __init bpf_fs_kfuncs_init(void) +{ + return register_btf_kfunc_id_set(BPF_PROG_TYPE_LSM, &bpf_fs_kfunc_set); +} + +late_initcall(bpf_fs_kfuncs_init); + static const struct bpf_func_proto * bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) {