On Wed, Jun 26, 2024 at 6:46 AM Benjamin Tissoires <bentiss@xxxxxxxxxx> wrote:
>
> This allows to intercept and prevent or change the behavior of
> hid_hw_raw_request() from a bpf program.
>
> The intent is to solve a couple of use case:
> - firewalling a HID device: a firewall can monitor who opens the hidraw
> nodes and then prevent or allow access to write operations on that
> hidraw node.
> - change the behavior of a device and emulate a new HID feature request
>
> The hook is allowed to be run as sleepable so it can itself call
> hid_bpf_hw_request(), which allows to "convert" one feature request into
> another or even call the feature request on a different HID device on the
> same physical device.
>
> Signed-off-by: Benjamin Tissoires <bentiss@xxxxxxxxxx>
>
> ---
>
> changes in v2:
> - make use of SRCU
> ---
> drivers/hid/bpf/hid_bpf_dispatch.c | 37 ++++++++++++++++++++++++++++++++++++
> drivers/hid/bpf/hid_bpf_struct_ops.c | 1 +
> drivers/hid/hid-core.c | 6 ++++++
> include/linux/hid_bpf.h | 35 ++++++++++++++++++++++++++++++++++
> 4 files changed, 79 insertions(+)
>
> diff --git a/drivers/hid/bpf/hid_bpf_dispatch.c b/drivers/hid/bpf/hid_bpf_dispatch.c
> index c026248e3d73..ac98bab4c96d 100644
> --- a/drivers/hid/bpf/hid_bpf_dispatch.c
> +++ b/drivers/hid/bpf/hid_bpf_dispatch.c
> @@ -74,6 +74,43 @@ dispatch_hid_bpf_device_event(struct hid_device *hdev, enum hid_report_type type
> }
> EXPORT_SYMBOL_GPL(dispatch_hid_bpf_device_event);
>
> +int dispatch_hid_bpf_raw_requests(struct hid_device *hdev,
> + unsigned char reportnum, u8 *buf,
> + u32 size, enum hid_report_type rtype,
> + enum hid_class_request reqtype,
> + u64 source)
> +{
> + struct hid_bpf_ctx_kern ctx_kern = {
> + .ctx = {
> + .hid = hdev,
> + .allocated_size = size,
> + .size = size,
> + },
> + .data = buf,
> + };
> + struct hid_bpf_ops *e;
> + int ret, idx;
> +
> + if (rtype >= HID_REPORT_TYPES)
> + return -EINVAL;
> +
> + idx = srcu_read_lock(&hdev->bpf.srcu);
> + list_for_each_entry_srcu(e, &hdev->bpf.prog_list, list,
> + srcu_read_lock_held(&hdev->bpf.srcu)) {
> + if (e->hid_hw_request) {
> + ret = e->hid_hw_request(&ctx_kern.ctx, reportnum, rtype, reqtype, source);
> + if (ret)
> + goto out;
> + }
> + }
here and in patch 7 I would reduce indent by doing:
if (!e->hid_hw_request)
continue;
ret = e->hid_hw_request(...);
otherwise lgtm
