[PATCH bpf-next v2 03/28] HID: hook up with bpf

Benjamin Tissoires
2022-03-04T17:31:17Z

Now that BPF can be compatible with HID, add the capability into HID.
drivers/hid/hid-bpf.c takes care of the glue between bpf and HID, and
hid-core can then inject any incoming event from the device into a BPF
program to filter/analyze it.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

---

changes in v2:
- split the series by bpf/libbpf/hid/selftests and samples
- addressed review comments from v1
---
drivers/hid/Makefile | 1 +
drivers/hid/hid-bpf.c | 157 +++++++++++++++++++++++++++++++++++++++++
drivers/hid/hid-core.c | 21 +++++-
include/linux/hid.h | 11 +++
4 files changed, 187 insertions(+), 3 deletions(-)
create mode 100644 drivers/hid/hid-bpf.c

diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
index 6d3e630e81af..08d2d7619937 100644
--- a/drivers/hid/Makefile
+++ b/drivers/hid/Makefile
@@ -4,6 +4,7 @@
#
hid-y := hid-core.o hid-input.o hid-quirks.o
hid-$(CONFIG_DEBUG_FS) += hid-debug.o
+hid-$(CONFIG_BPF) += hid-bpf.o

obj-$(CONFIG_HID) += hid.o
obj-$(CONFIG_UHID) += uhid.o
diff --git a/drivers/hid/hid-bpf.c b/drivers/hid/hid-bpf.c
new file mode 100644
index 000000000000..8120e598de9f
--- /dev/null
+++ b/drivers/hid/hid-bpf.c
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * BPF in HID support for Linux
+ *
+ * Copyright (c) 2022 Benjamin Tissoires
+ */
+
+#include <linux/filter.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+
+#include <uapi/linux/bpf_hid.h>
+#include <linux/hid.h>
+
+static int __hid_bpf_match_sysfs(struct device *dev, const void *data)
+{
+ struct kernfs_node *kn = dev->kobj.sd;
+ struct kernfs_node *uevent_kn;
+
+ uevent_kn = kernfs_find_and_get_ns(kn, "uevent", NULL);
+
+ return uevent_kn == data;
+}
+
+static struct hid_device *hid_bpf_fd_to_hdev(int fd)
+{
+ struct device *dev;
+ struct hid_device *hdev;
+ struct fd f = fdget(fd);
+ struct inode *inode;
+ struct kernfs_node *node;
+
+ if (!f.file) {
+ hdev = ERR_PTR(-EBADF);
+ goto out;
+ }
+
+ inode = file_inode(f.file);
+ node = inode->i_private;
+
+ dev = bus_find_device(&hid_bus_type, NULL, node, __hid_bpf_match_sysfs);
+
+ if (dev)
+ hdev = to_hid_device(dev);
+ else
+ hdev = ERR_PTR(-EINVAL);
+
+ out:
+ fdput(f);
+ return hdev;
+}
+
+static int hid_bpf_link_attach(struct hid_device *hdev, enum bpf_hid_attach_type type)
+{
+ int err = 0;
+
+ switch (type) {
+ case BPF_HID_ATTACH_DEVICE_EVENT:
+ if (!hdev->bpf.ctx) {
+ hdev->bpf.ctx = bpf_hid_allocate_ctx(hdev, HID_BPF_MAX_BUFFER_SIZE);
+ if (IS_ERR(hdev->bpf.ctx)) {
+ err = PTR_ERR(hdev->bpf.ctx);
+ hdev->bpf.ctx = NULL;
+ }
+ }
+ break;
+ default:
+ /* do nothing */
+ }
+
+ return err;
+}
+
+static void hid_bpf_array_detached(struct hid_device *hdev, enum bpf_hid_attach_type type)
+{
+ switch (type) {
+ case BPF_HID_ATTACH_DEVICE_EVENT:
+ kfree(hdev->bpf.ctx);
+ hdev->bpf.ctx = NULL;
+ break;
+ default:
+ /* do nothing */
+ }
+}
+
+static int hid_bpf_run_progs(struct hid_device *hdev, enum bpf_hid_attach_type type,
+ struct hid_bpf_ctx *ctx, u8 *data, int size)
+{
+ enum hid_bpf_event event = HID_BPF_UNDEF;
+
+ if (type < 0 || !ctx)
+ return -EINVAL;
+
+ if (size > ctx->allocated_size)
+ return -E2BIG;
+
+ switch (type) {
+ case BPF_HID_ATTACH_DEVICE_EVENT:
+ event = HID_BPF_DEVICE_EVENT;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ if (!hdev->bpf.run_array[type])
+ return 0;
+
+ memset(ctx->data, 0, ctx->allocated_size);
+ ctx->type = event;
+
+ if (size && data) {
+ memcpy(ctx->data, data, size);
+ ctx->size = size;
+ } else {
+ ctx->size = 0;
+ }
+
+ return BPF_PROG_RUN_ARRAY(hdev->bpf.run_array[type], ctx, bpf_prog_run);
+}
+
+u8 *hid_bpf_raw_event(struct hid_device *hdev, u8 *data, int *size)
+{
+ int ret;
+
+ if (bpf_hid_link_empty(&hdev->bpf, BPF_HID_ATTACH_DEVICE_EVENT))
+ return data;
+
+ ret = hid_bpf_run_progs(hdev, BPF_HID_ATTACH_DEVICE_EVENT,
+ hdev->bpf.ctx, data, *size);
+ if (ret)
+ return ERR_PTR(ret);
+
+ if (!hdev->bpf.ctx->size)
+ return ERR_PTR(-EINVAL);
+
+ *size = hdev->bpf.ctx->size;
+
+ return hdev->bpf.ctx->data;
+}
+
+int __init hid_bpf_module_init(void)
+{
+ struct bpf_hid_hooks hooks = {
+ .hdev_from_fd = hid_bpf_fd_to_hdev,
+ .link_attach = hid_bpf_link_attach,
+ .array_detached = hid_bpf_array_detached,
+ };
+
+ bpf_hid_set_hooks(&hooks);
+
+ return 0;
+}
+
+void __exit hid_bpf_module_exit(void)
+{
+ bpf_hid_set_hooks(NULL);
+}
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index f1aed5bbd000..a80bffe6ce4a 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -1748,13 +1748,21 @@ int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, u32 size,
struct hid_driver *hdrv;
unsigned int a;
u32 rsize, csize = size;
- u8 *cdata = data;
+ u8 *cdata;
int ret = 0;

+ data = hid_bpf_raw_event(hid, data, &size);
+ if (IS_ERR(data)) {
+ ret = PTR_ERR(data);
+ goto out;
+ }
+
report = hid_get_report(report_enum, data);
if (!report)
goto out;

+ cdata = data;
+
if (report_enum->numbered) {
cdata++;
csize--;
@@ -2528,10 +2536,12 @@ int hid_add_device(struct hid_device *hdev)

hid_debug_register(hdev, dev_name(&hdev->dev));
ret = device_add(&hdev->dev);
- if (!ret)
+ if (!ret) {
hdev->status |= HID_STAT_ADDED;
- else
+ } else {
hid_debug_unregister(hdev);
+ bpf_hid_exit(hdev);
+ }

return ret;
}
@@ -2567,6 +2577,7 @@ struct hid_device *hid_allocate_device(void)
spin_lock_init(&hdev->debug_list_lock);
sema_init(&hdev->driver_input_lock, 1);
mutex_init(&hdev->ll_open_lock);
+ bpf_hid_init(hdev);

return hdev;
}
@@ -2574,6 +2585,7 @@ EXPORT_SYMBOL_GPL(hid_allocate_device);

static void hid_remove_device(struct hid_device *hdev)
{
+ bpf_hid_exit(hdev);
if (hdev->status & HID_STAT_ADDED) {
device_del(&hdev->dev);
hid_debug_unregister(hdev);
@@ -2700,6 +2712,8 @@ static int __init hid_init(void)

hid_debug_init();

+ hid_bpf_module_init();
+
return 0;
err_bus:
bus_unregister(&hid_bus_type);
@@ -2709,6 +2723,7 @@ static int __init hid_init(void)

static void __exit hid_exit(void)
{
+ hid_bpf_module_exit();
hid_debug_exit();
hidraw_exit();
bus_unregister(&hid_bus_type);
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 56f6f4ad45a7..8fd79011f461 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -27,6 +27,7 @@
#include <linux/mutex.h>
#include <linux/power_supply.h>
#include <uapi/linux/hid.h>
+#include <uapi/linux/bpf_hid.h>

/*
* We parse each description item into this structure. Short items data
@@ -1210,4 +1211,14 @@ do { \
#define hid_dbg_once(hid, fmt, ...) \
dev_dbg_once(&(hid)->dev, fmt, ##__VA_ARGS__)

+#ifdef CONFIG_BPF
+u8 *hid_bpf_raw_event(struct hid_device *hdev, u8 *rd, int *size);
+int hid_bpf_module_init(void);
+void hid_bpf_module_exit(void);
+#else
+static inline u8 *hid_bpf_raw_event(struct hid_device *hdev, u8 *rd, int *size) { return rd; }
+static inline int hid_bpf_module_init(void) { return 0; }
+static inline void hid_bpf_module_exit(void) {}
+#endif
+
#endif
--
2.35.1