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HID: bpf: add HID-BPF hooks for hid_hw_output_report

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Same story than hid_hw_raw_requests:

This allows to intercept and prevent or change the behavior of
hid_hw_output_report() 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_hw_output_report(), 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.

Link: https://patch.msgid.link/20240626-hid_hw_req_bpf-v2-7-cfd60fb6c79f@kernel.org
Acked-by: Jiri Kosina <jkosina@suse.com>
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
This commit is contained in:
Benjamin Tissoires
2024-06-26 15:46:28 +02:00
parent 015a4a2a43
commit 9286675a2a
6 changed files with 70 additions and 9 deletions
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24
include/linux/hid_bpf.h
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@@ -70,7 +70,7 @@ struct hid_ops {
enum hid_class_request reqtype,
__u64 source, bool from_bpf);
int (*hid_hw_output_report)(struct hid_device *hdev, __u8 *buf, size_t len,
__u64 source);
__u64 source, bool from_bpf);
int (*hid_input_report)(struct hid_device *hid, enum hid_report_type type,
u8 *data, u32 size, int interrupt, u64 source);
struct module *owner;
@@ -154,6 +154,24 @@ struct hid_bpf_ops {
enum hid_report_type rtype, enum hid_class_request reqtype,
__u64 source);
/**
* @hid_hw_output_report: called whenever a hid_hw_output_report() call is emitted
* on the HID device
*
* It has the following arguments:
*
* ``ctx``: The HID-BPF context as &struct hid_bpf_ctx
* ``source``: a u64 referring to a uniq but identifiable source. If %0, the
* kernel itself emitted that call. For hidraw, ``source`` is set
* to the associated ``struct file *``.
*
* Return: %0 to keep processing the request by hid-core; any other value
* stops hid-core from processing that event. A positive value should be
* returned with the number of bytes written to the device; a negative error
* code interrupts the processing of this call.
*/
int (*hid_hw_output_report)(struct hid_bpf_ctx *ctx, __u64 source);
/* private: do not show up in the docs */
struct hid_device *hdev;
@@ -182,6 +200,8 @@ int dispatch_hid_bpf_raw_requests(struct hid_device *hdev,
u32 size, enum hid_report_type rtype,
enum hid_class_request reqtype,
__u64 source, bool from_bpf);
int dispatch_hid_bpf_output_report(struct hid_device *hdev, __u8 *buf, u32 size,
__u64 source, bool from_bpf);
int hid_bpf_connect_device(struct hid_device *hdev);
void hid_bpf_disconnect_device(struct hid_device *hdev);
void hid_bpf_destroy_device(struct hid_device *hid);
@@ -196,6 +216,8 @@ static inline int dispatch_hid_bpf_raw_requests(struct hid_device *hdev,
u32 size, enum hid_report_type rtype,
enum hid_class_request reqtype,
u64 source, bool from_bpf) { return 0; }
static inline int dispatch_hid_bpf_output_report(struct hid_device *hdev, __u8 *buf, u32 size,
__u64 source, bool from_bpf) { return 0; }
static inline int hid_bpf_connect_device(struct hid_device *hdev) { return 0; }
static inline void hid_bpf_disconnect_device(struct hid_device *hdev) {}
static inline void hid_bpf_destroy_device(struct hid_device *hid) {}