HID: bpf: protect HID-BPF prog_list access by a SRCU

We want to add sleepable callbacks for hid_hw_raw_request() and
hid_hw_output_report(), but we can not use a plain RCU for those.

Prepare for a SRCU so we can extend HID-BPF.

This changes a little bit how hid_bpf_device_init() behaves, as it may
now fail, so there is a tiny hid-core.c change to accommodate for this.

Link: https://patch.msgid.link/20240626-hid_hw_req_bpf-v2-3-cfd60fb6c79f@kernel.org
Acked-by: Jiri Kosina <jkosina@suse.com>
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

3 files changed, 14 insertions, 2 deletions

diff --git a/drivers/hid/bpf/hid_bpf_dispatch.c b/drivers/hid/bpf/hid_bpf_dispatch.c
index 2df31decaac3..c026248e3d73 100644
--- a/drivers/hid/bpf/hid_bpf_dispatch.c
+++ b/drivers/hid/bpf/hid_bpf_dispatch.c
@@ -506,13 +506,17 @@ void hid_bpf_destroy_device(struct hid_device *hdev)
 	hdev->bpf.destroyed = true;
 
 	__hid_bpf_ops_destroy_device(hdev);
+
+	synchronize_srcu(&hdev->bpf.srcu);
+	cleanup_srcu_struct(&hdev->bpf.srcu);
 }
 EXPORT_SYMBOL_GPL(hid_bpf_destroy_device);
 
-void hid_bpf_device_init(struct hid_device *hdev)
+int hid_bpf_device_init(struct hid_device *hdev)
 {
 	INIT_LIST_HEAD(&hdev->bpf.prog_list);
 	mutex_init(&hdev->bpf.prog_list_lock);
+	return init_srcu_struct(&hdev->bpf.srcu);
 }
 EXPORT_SYMBOL_GPL(hid_bpf_device_init);
 
diff --git a/drivers/hid/bpf/hid_bpf_struct_ops.c b/drivers/hid/bpf/hid_bpf_struct_ops.c
index 8063db1c8d62..d34731a1b457 100644
--- a/drivers/hid/bpf/hid_bpf_struct_ops.c
+++ b/drivers/hid/bpf/hid_bpf_struct_ops.c
@@ -214,6 +214,7 @@ static int hid_bpf_reg(void *kdata)
 		list_add_rcu(&ops->list, &hdev->bpf.prog_list);
 	else
 		list_add_tail_rcu(&ops->list, &hdev->bpf.prog_list);
+	synchronize_srcu(&hdev->bpf.srcu);
 
 out_unlock:
 	mutex_unlock(&hdev->bpf.prog_list_lock);
@@ -244,6 +245,7 @@ static void hid_bpf_unreg(void *kdata)
 	mutex_lock(&hdev->bpf.prog_list_lock);
 
 	list_del_rcu(&ops->list);
+	synchronize_srcu(&hdev->bpf.srcu);
 
 	reconnect = hdev->bpf.rdesc_ops == ops;
 	if (reconnect)
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 0775a32f5272..ad08289752da 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2875,9 +2875,15 @@ struct hid_device *hid_allocate_device(void)
 	mutex_init(&hdev->ll_open_lock);
 	kref_init(&hdev->ref);
 
-	hid_bpf_device_init(hdev);
+	ret = hid_bpf_device_init(hdev);
+	if (ret)
+		goto out_err;
 
 	return hdev;
+
+out_err:
+	hid_destroy_device(hdev);
+	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL_GPL(hid_allocate_device);