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Sun, 29 Mar 2026 07:05:38 -0700 (PDT) From: Chengkaitao To: martin.lau@linux.dev, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, chengkaitao@kylinos.cn, linux-kselftest@vger.kernel.org Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH bpf-next v9 3/9] bpf: clear list node owner and unlink before drop Date: Sun, 29 Mar 2026 22:05:00 +0800 Message-ID: <20260329140506.9595-4-pilgrimtao@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260329140506.9595-1-pilgrimtao@gmail.com> References: <20260329140506.9595-1-pilgrimtao@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Kaitao Cheng When draining a BPF list_head, clear each node's owner pointer while still holding the spinlock, so concurrent readers always see a consistent owner. Delink each node with list_del_init() before calling __bpf_obj_drop_impl(), preventing subsequent users who hold a reference count to the node from acquiring an invalid next node. Signed-off-by: Kaitao Cheng --- kernel/bpf/helpers.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 94fcd4ab39e9..8abb99712043 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2232,7 +2232,7 @@ EXPORT_SYMBOL_GPL(bpf_base_func_proto); void bpf_list_head_free(const struct btf_field *field, void *list_head, struct bpf_spin_lock *spin_lock) { - struct list_head *head =3D list_head, *orig_head =3D list_head; + struct list_head *head =3D list_head, *orig_head =3D list_head, *pos; =20 BUILD_BUG_ON(sizeof(struct list_head) > sizeof(struct bpf_list_head)); BUILD_BUG_ON(__alignof__(struct list_head) > __alignof__(struct bpf_list_= head)); @@ -2247,6 +2247,9 @@ void bpf_list_head_free(const struct btf_field *field= , void *list_head, if (!head->next || list_empty(head)) goto unlock; head =3D head->next; + /* Clear owner under spinlock to ensure the owner is always valid */ + for (pos =3D head; pos !=3D orig_head; pos =3D pos->next) + WRITE_ONCE(container_of(pos, struct bpf_list_node_kern, list_head)->owne= r, NULL); unlock: INIT_LIST_HEAD(orig_head); __bpf_spin_unlock_irqrestore(spin_lock); @@ -2255,7 +2258,9 @@ void bpf_list_head_free(const struct btf_field *field= , void *list_head, void *obj =3D head; =20 obj -=3D field->graph_root.node_offset; + pos =3D head; head =3D head->next; + list_del_init(pos); /* The contained type can also have resources, including a * bpf_list_head which needs to be freed. */ --=20 2.50.1 (Apple Git-155)