linux-kernel - [PATCH bpf-next 3/4] bpf: Mark cgroup_subsys

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Message-ID: <20250618233739.189106-4-song@kernel.org>
Date: Wed, 18 Jun 2025 16:37:38 -0700
From: Song Liu <song@...nel.org>
To: bpf@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org
Cc: kernel-team@...a.com,
	andrii@...nel.org,
	eddyz87@...il.com,
	ast@...nel.org,
	daniel@...earbox.net,
	martin.lau@...ux.dev,
	viro@...iv.linux.org.uk,
	brauner@...nel.org,
	jack@...e.cz,
	kpsingh@...nel.org,
	mattbobrowski@...gle.com,
	amir73il@...il.com,
	gregkh@...uxfoundation.org,
	tj@...nel.org,
	daan.j.demeyer@...il.com,
	Song Liu <song@...nel.org>
Subject: [PATCH bpf-next 3/4] bpf: Mark cgroup_subsys_state->cgroup RCU safe

Mark struct cgroup_subsys_state->cgroup as safe under RCU read lock. This
will enable accessing css->cgroup from a bpf css iterator.

Signed-off-by: Song Liu <song@...nel.org>
---
 kernel/bpf/verifier.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 279a64933262..e2f53dc8766a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7058,6 +7058,10 @@ BTF_TYPE_SAFE_RCU(struct css_set) {
 	struct cgroup *dfl_cgrp;
 };
 
+BTF_TYPE_SAFE_RCU(struct cgroup_subsys_state) {
+	struct cgroup *cgroup;
+};
+
 /* RCU trusted: these fields are trusted in RCU CS and can be NULL */
 BTF_TYPE_SAFE_RCU_OR_NULL(struct mm_struct) {
 	struct file __rcu *exe_file;
@@ -7108,6 +7112,7 @@ static bool type_is_rcu(struct bpf_verifier_env *env,
 	BTF_TYPE_EMIT(BTF_TYPE_SAFE_RCU(struct task_struct));
 	BTF_TYPE_EMIT(BTF_TYPE_SAFE_RCU(struct cgroup));
 	BTF_TYPE_EMIT(BTF_TYPE_SAFE_RCU(struct css_set));
+	BTF_TYPE_EMIT(BTF_TYPE_SAFE_RCU(struct cgroup_subsys_state));
 
 	return btf_nested_type_is_trusted(&env->log, reg, field_name, btf_id, "__safe_rcu");
 }
-- 
2.47.1