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.
Signed-off-by: Benjamin Tissoires bentiss@kernel.org
---
changes in v2: - make use of SRCU --- drivers/hid/bpf/hid_bpf_dispatch.c | 38 ++++++++++++++++++++++++++++++++---- drivers/hid/bpf/hid_bpf_struct_ops.c | 1 + drivers/hid/hid-core.c | 10 ++++++++-- drivers/hid/hidraw.c | 2 +- include/linux/hid.h | 3 ++- include/linux/hid_bpf.h | 24 ++++++++++++++++++++++- 6 files changed, 69 insertions(+), 9 deletions(-)
diff --git a/drivers/hid/bpf/hid_bpf_dispatch.c b/drivers/hid/bpf/hid_bpf_dispatch.c index 80c6787195f7..49f261054418 100644 --- a/drivers/hid/bpf/hid_bpf_dispatch.c +++ b/drivers/hid/bpf/hid_bpf_dispatch.c @@ -112,6 +112,39 @@ int dispatch_hid_bpf_raw_requests(struct hid_device *hdev, } EXPORT_SYMBOL_GPL(dispatch_hid_bpf_raw_requests);
+int dispatch_hid_bpf_output_report(struct hid_device *hdev, + __u8 *buf, u32 size, __u64 source, + bool from_bpf) +{ + struct hid_bpf_ctx_kern ctx_kern = { + .ctx = { + .hid = hdev, + .allocated_size = size, + .size = size, + }, + .data = buf, + .from_bpf = from_bpf, + }; + struct hid_bpf_ops *e; + int ret, idx; + + 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_output_report) { + ret = e->hid_hw_output_report(&ctx_kern.ctx, source); + if (ret) + goto out; + } + } + ret = 0; + +out: + srcu_read_unlock(&hdev->bpf.srcu, idx); + return ret; +} +EXPORT_SYMBOL_GPL(dispatch_hid_bpf_output_report); + u8 *call_hid_bpf_rdesc_fixup(struct hid_device *hdev, u8 *rdesc, unsigned int *size) { int ret; @@ -442,10 +475,7 @@ hid_bpf_hw_output_report(struct hid_bpf_ctx *ctx, __u8 *buf, size_t buf__sz) if (!dma_data) return -ENOMEM;
- ret = hid_ops->hid_hw_output_report(hdev, - dma_data, - size, - (__u64)ctx); + ret = hid_ops->hid_hw_output_report(hdev, dma_data, size, (__u64)ctx, true);
kfree(dma_data); return ret; diff --git a/drivers/hid/bpf/hid_bpf_struct_ops.c b/drivers/hid/bpf/hid_bpf_struct_ops.c index a540a4417174..37d2f8e2413a 100644 --- a/drivers/hid/bpf/hid_bpf_struct_ops.c +++ b/drivers/hid/bpf/hid_bpf_struct_ops.c @@ -45,6 +45,7 @@ static int hid_bpf_ops_check_member(const struct btf_type *t, switch (moff) { case offsetof(struct hid_bpf_ops, hid_rdesc_fixup): case offsetof(struct hid_bpf_ops, hid_hw_request): + case offsetof(struct hid_bpf_ops, hid_hw_output_report): break; default: if (prog->sleepable) diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index 2038ba08eaa1..bb6f334f05bd 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -2445,9 +2445,11 @@ int hid_hw_raw_request(struct hid_device *hdev, } EXPORT_SYMBOL_GPL(hid_hw_raw_request);
-int __hid_hw_output_report(struct hid_device *hdev, __u8 *buf, size_t len, __u64 source) +int __hid_hw_output_report(struct hid_device *hdev, __u8 *buf, size_t len, __u64 source, + bool from_bpf) { unsigned int max_buffer_size = HID_MAX_BUFFER_SIZE; + int ret;
if (hdev->ll_driver->max_buffer_size) max_buffer_size = hdev->ll_driver->max_buffer_size; @@ -2455,6 +2457,10 @@ int __hid_hw_output_report(struct hid_device *hdev, __u8 *buf, size_t len, __u64 if (len < 1 || len > max_buffer_size || !buf) return -EINVAL;
+ ret = dispatch_hid_bpf_output_report(hdev, buf, len, source, from_bpf); + if (ret) + return ret; + if (hdev->ll_driver->output_report) return hdev->ll_driver->output_report(hdev, buf, len);
@@ -2472,7 +2478,7 @@ int __hid_hw_output_report(struct hid_device *hdev, __u8 *buf, size_t len, __u64 */ int hid_hw_output_report(struct hid_device *hdev, __u8 *buf, size_t len) { - return __hid_hw_output_report(hdev, buf, len, 0); + return __hid_hw_output_report(hdev, buf, len, 0, false); } EXPORT_SYMBOL_GPL(hid_hw_output_report);
diff --git a/drivers/hid/hidraw.c b/drivers/hid/hidraw.c index 4ba3131de614..c2396916cdaa 100644 --- a/drivers/hid/hidraw.c +++ b/drivers/hid/hidraw.c @@ -140,7 +140,7 @@ static ssize_t hidraw_send_report(struct file *file, const char __user *buffer,
if ((report_type == HID_OUTPUT_REPORT) && !(dev->quirks & HID_QUIRK_NO_OUTPUT_REPORTS_ON_INTR_EP)) { - ret = __hid_hw_output_report(dev, buf, count, (__u64)file); + ret = __hid_hw_output_report(dev, buf, count, (__u64)file, false); /* * compatibility with old implementation of USB-HID and I2C-HID: * if the device does not support receiving output reports, diff --git a/include/linux/hid.h b/include/linux/hid.h index 24d0d7c0bd33..1533c9dcd3a6 100644 --- a/include/linux/hid.h +++ b/include/linux/hid.h @@ -1130,7 +1130,8 @@ int __hid_hw_raw_request(struct hid_device *hdev, size_t len, enum hid_report_type rtype, 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); +int __hid_hw_output_report(struct hid_device *hdev, __u8 *buf, size_t len, __u64 source, + bool from_bpf); int hid_hw_raw_request(struct hid_device *hdev, unsigned char reportnum, __u8 *buf, size_t len, enum hid_report_type rtype, diff --git a/include/linux/hid_bpf.h b/include/linux/hid_bpf.h index 088c94b6d8ec..f35508a73067 100644 --- a/include/linux/hid_bpf.h +++ b/include/linux/hid_bpf.h @@ -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) {}