[PATCH bpf-next v2 15/28] bpf/hid: add new BPF type to trigger commands from userspace

Benjamin Tissoires
2022-03-04T17:33:47Z

Given that we can not call bpf_hid_raw_request() from within an IRQ,
userspace needs to have a way to communicate with the device when
it needs.

Implement a new type that the caller can run at will without being in
an IRQ context.

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

---

changes in v2:
- split the series by bpf/libbpf/hid/selftests and samples
- unsigned long -> __u16 in uapi/linux/bpf_hid.h
- int -> __32 in uapi/linux/bpf_hid.h
---
include/linux/bpf-hid.h | 3 +
include/uapi/linux/bpf.h | 1 +
include/uapi/linux/bpf_hid.h | 10 +++
kernel/bpf/hid.c | 116 +++++++++++++++++++++++++++++++++
kernel/bpf/syscall.c | 2 +
tools/include/uapi/linux/bpf.h | 1 +
6 files changed, 133 insertions(+)

diff --git a/include/linux/bpf-hid.h b/include/linux/bpf-hid.h
index 69bb28523ceb..4cf2e99109fe 100644
--- a/include/linux/bpf-hid.h
+++ b/include/linux/bpf-hid.h
@@ -16,6 +16,7 @@ enum bpf_hid_attach_type {
BPF_HID_ATTACH_INVALID = -1,
BPF_HID_ATTACH_DEVICE_EVENT = 0,
BPF_HID_ATTACH_RDESC_FIXUP,
+ BPF_HID_ATTACH_USER_EVENT,
MAX_BPF_HID_ATTACH_TYPE
};

@@ -35,6 +36,8 @@ to_bpf_hid_attach_type(enum bpf_attach_type attach_type)
return BPF_HID_ATTACH_DEVICE_EVENT;
case BPF_HID_RDESC_FIXUP:
return BPF_HID_ATTACH_RDESC_FIXUP;
+ case BPF_HID_USER_EVENT:
+ return BPF_HID_ATTACH_USER_EVENT;
default:
return BPF_HID_ATTACH_INVALID;
}
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 4845a20e6f96..b3063384d380 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1000,6 +1000,7 @@ enum bpf_attach_type {
BPF_PERF_EVENT,
BPF_HID_DEVICE_EVENT,
BPF_HID_RDESC_FIXUP,
+ BPF_HID_USER_EVENT,
__MAX_BPF_ATTACH_TYPE
};

diff --git a/include/uapi/linux/bpf_hid.h b/include/uapi/linux/bpf_hid.h
index 634f17c0b1cb..14a3c0405345 100644
--- a/include/uapi/linux/bpf_hid.h
+++ b/include/uapi/linux/bpf_hid.h
@@ -25,6 +25,12 @@ enum hid_bpf_event {
HID_BPF_UNDEF = 0,
HID_BPF_DEVICE_EVENT, /* when attach type is BPF_HID_DEVICE_EVENT */
HID_BPF_RDESC_FIXUP, /* ................... BPF_HID_RDESC_FIXUP */
+ HID_BPF_USER_EVENT, /* ................... BPF_HID_USER_EVENT */
+};
+
+/* type is HID_BPF_USER_EVENT */
+struct hid_bpf_ctx_user_event {
+ __s32 retval;
};

struct hid_bpf_ctx {
@@ -32,6 +38,10 @@ struct hid_bpf_ctx {
__u16 allocated_size; /* the allocated size of data below (RO) */
struct hid_device *hdev; /* read-only */

+ union {
+ struct hid_bpf_ctx_user_event user; /* read-write */
+ } u;
+
__u16 size; /* used size in data (RW) */
__u8 data[]; /* data buffer (RW) */
};
diff --git a/kernel/bpf/hid.c b/kernel/bpf/hid.c
index 640e55ba66ec..de003dbd7d01 100644
--- a/kernel/bpf/hid.c
+++ b/kernel/bpf/hid.c
@@ -370,6 +370,8 @@ static int bpf_hid_max_progs(enum bpf_hid_attach_type type)
return 64;
case BPF_HID_ATTACH_RDESC_FIXUP:
return 1;
+ case BPF_HID_ATTACH_USER_EVENT:
+ return 64;
default:
return 0;
}
@@ -464,7 +466,121 @@ int bpf_hid_link_create(const union bpf_attr *attr, struct bpf_prog *prog)
return bpf_link_settle(&link_primer);
}

+static int hid_bpf_prog_test_run(struct bpf_prog *prog,
+ const union bpf_attr *attr,
+ union bpf_attr __user *uattr)
+{
+ struct hid_device *hdev = NULL;
+ struct bpf_prog_array *progs;
+ struct hid_bpf_ctx *ctx = NULL;
+ bool valid_prog = false;
+ int i;
+ int target_fd, ret;
+ void __user *data_out = u64_to_user_ptr(attr->test.data_out);
+ void __user *data_in = u64_to_user_ptr(attr->test.data_in);
+ u32 user_size_in = attr->test.data_size_in;
+ u32 user_size_out = attr->test.data_size_out;
+
+ if (!hid_hooks.hdev_from_fd)
+ return -EOPNOTSUPP;
+
+ if (attr->test.ctx_size_in != sizeof(int))
+ return -EINVAL;
+
+ if (user_size_in > HID_BPF_MAX_BUFFER_SIZE)
+ return -E2BIG;
+
+ if (copy_from_user(&target_fd, (void *)attr->test.ctx_in, attr->test.ctx_size_in))
+ return -EFAULT;
+
+ hdev = hid_hooks.hdev_from_fd(target_fd);
+ if (IS_ERR(hdev))
+ return PTR_ERR(hdev);
+
+ ret = mutex_lock_interruptible(&bpf_hid_mutex);
+ if (ret)
+ return ret;
+
+ /* check if the given program is of correct type and registered */
+ progs = rcu_dereference_protected(hdev->bpf.run_array[BPF_HID_ATTACH_USER_EVENT],
+ lockdep_is_held(&bpf_hid_mutex));
+ if (!progs) {
+ ret = -EFAULT;
+ goto unlock;
+ }
+
+ for (i = 0; i < bpf_prog_array_length(progs); i++) {
+ if (progs->items[i].prog == prog) {
+ valid_prog = true;
+ break;
+ }
+ }
+
+ if (!valid_prog) {
+ ret = -EINVAL;
+ goto unlock;
+ }
+
+ ctx = bpf_hid_allocate_ctx(hdev, max(user_size_in, user_size_out));
+ if (IS_ERR(ctx)) {
+ ret = PTR_ERR(ctx);
+ goto unlock;
+ }
+
+ ctx->type = HID_BPF_USER_EVENT;
+
+ /* copy data_in from userspace */
+ if (user_size_in) {
+ if (user_size_in > ctx->allocated_size) {
+ /* should never happen, given that size is < HID_BPF_MAX_BUFFER_SIZE */
+ ret = -E2BIG;
+ goto unlock;
+ }
+
+ if (copy_from_user(ctx->data, data_in, user_size_in)) {
+ ret = -EFAULT;
+ goto unlock;
+ }
+
+ ctx->size = user_size_in;
+ }
+
+ migrate_disable();
+
+ ret = bpf_prog_run(prog, ctx);
+
+ migrate_enable();
+
+ if (user_size_out && data_out) {
+ user_size_out = min3(user_size_out, (u32)ctx->size, (u32)ctx->allocated_size);
+
+ if (copy_to_user(data_out, ctx->data, user_size_out)) {
+ ret = -EFAULT;
+ goto unlock;
+ }
+
+ if (copy_to_user(&uattr->test.data_size_out,
+ &user_size_out,
+ sizeof(user_size_out))) {
+ ret = -EFAULT;
+ goto unlock;
+ }
+ }
+
+ if (copy_to_user(&uattr->test.retval, &ctx->u.user.retval, sizeof(ctx->u.user.retval))) {
+ ret = -EFAULT;
+ goto unlock;
+ }
+
+unlock:
+ kfree(ctx);
+
+ mutex_unlock(&bpf_hid_mutex);
+ return ret;
+}
+
const struct bpf_prog_ops hid_prog_ops = {
+ .test_run = hid_bpf_prog_test_run,
};

int bpf_hid_init(struct hid_device *hdev)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 7428a1a512c6..74d13ec826df 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3204,6 +3204,7 @@ attach_type_to_prog_type(enum bpf_attach_type attach_type)
return BPF_PROG_TYPE_XDP;
case BPF_HID_DEVICE_EVENT:
case BPF_HID_RDESC_FIXUP:
+ case BPF_HID_USER_EVENT:
return BPF_PROG_TYPE_HID;
default:
return BPF_PROG_TYPE_UNSPEC;
@@ -3350,6 +3351,7 @@ static int bpf_prog_query(const union bpf_attr *attr,
return sock_map_bpf_prog_query(attr, uattr);
case BPF_HID_DEVICE_EVENT:
case BPF_HID_RDESC_FIXUP:
+ case BPF_HID_USER_EVENT:
return bpf_hid_prog_query(attr, uattr);
default:
return -EINVAL;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 4845a20e6f96..b3063384d380 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1000,6 +1000,7 @@ enum bpf_attach_type {
BPF_PERF_EVENT,
BPF_HID_DEVICE_EVENT,
BPF_HID_RDESC_FIXUP,
+ BPF_HID_USER_EVENT,
__MAX_BPF_ATTACH_TYPE
};

--
2.35.1