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@xxxxxxxxxx>
---
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) {}
--
2.44.0
