linux-kernel - [RFC PATCH v2 13/14] bpf: cgroup: Introduce helper cgroup_bpf_current

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Message-Id: <20231018105033.13669-14-michael.weiss@aisec.fraunhofer.de>
Date:   Wed, 18 Oct 2023 12:50:32 +0200
From:   Michael Weiß <michael.weiss@...ec.fraunhofer.de>
To:     Alexander Mikhalitsyn <alexander@...alicyn.com>,
        Christian Brauner <brauner@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Paul Moore <paul@...l-moore.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Quentin Monnet <quentin@...valent.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Miklos Szeredi <miklos@...redi.hu>,
        Amir Goldstein <amir73il@...il.com>,
        "Serge E. Hallyn" <serge@...lyn.com>, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        gyroidos@...ec.fraunhofer.de,
        Michael Weiß <michael.weiss@...ec.fraunhofer.de>,
        Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
Subject: [RFC PATCH v2 13/14] bpf: cgroup: Introduce helper cgroup_bpf_current_enabled()

This helper can be used to check if a cgroup-bpf specific program is
active for the current task.

Signed-off-by: Michael Weiß <michael.weiss@...ec.fraunhofer.de>
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
---
 include/linux/bpf-cgroup.h |  2 ++
 kernel/bpf/cgroup.c        | 14 ++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index 8506690dbb9c..655697c2a620 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -184,6 +184,8 @@ static inline bool cgroup_bpf_sock_enabled(struct sock *sk,
 	return array != &bpf_empty_prog_array.hdr;
 }
 
+bool cgroup_bpf_current_enabled(enum cgroup_bpf_attach_type type);
+
 /* Wrappers for __cgroup_bpf_run_filter_skb() guarded by cgroup_bpf_enabled. */
 #define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk, skb)			      \
 ({									      \
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 03b3d4492980..19ae3d037db7 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -24,6 +24,20 @@
 DEFINE_STATIC_KEY_ARRAY_FALSE(cgroup_bpf_enabled_key, MAX_CGROUP_BPF_ATTACH_TYPE);
 EXPORT_SYMBOL(cgroup_bpf_enabled_key);
 
+bool cgroup_bpf_current_enabled(enum cgroup_bpf_attach_type type)
+{
+	struct cgroup *cgrp;
+	struct bpf_prog_array *array;
+
+	rcu_read_lock();
+	cgrp = task_dfl_cgroup(current);
+	rcu_read_unlock();
+
+	array = rcu_access_pointer(cgrp->bpf.effective[type]);
+	return array != &bpf_empty_prog_array.hdr;
+}
+EXPORT_SYMBOL(cgroup_bpf_current_enabled);
+
 /* __always_inline is necessary to prevent indirect call through run_prog
  * function pointer.
  */
-- 
2.30.2