HID: bpf: make part of struct hid_device writable

It is useful to change the name, the phys and/or the uniq of a
struct hid_device during .rdesc_fixup().

For example, hid-uclogic.ko changes the uniq to store the firmware version
to differentiate between 2 devices sharing the same PID. In the same
way, changing the device name is useful when the device export 3 nodes,
all with the same name.

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Benjamin Tissoires <[email protected]>

Author: Benjamin Tissoires

drivers/hid/bpf/hid_bpf_struct_ops.c

@@ -74,6 +74,9 @@ static int hid_bpf_ops_btf_struct_access(struct bpf_verifier_log *log,
 
 	const struct hid_bpf_offset_write_range write_ranges[] = {
 		WRITE_RANGE(hid_bpf_ctx, retval, false),
+		WRITE_RANGE(hid_device, name, true),
+		WRITE_RANGE(hid_device, uniq, true),
+		WRITE_RANGE(hid_device, phys, true),
 	};
 #undef WRITE_RANGE
 	const struct btf_type *state = NULL;

include/linux/hid_bpf.h

@@ -43,7 +43,7 @@ struct hid_device;
  * ``hid`` and ``allocated_size`` are read-only, ``size`` and ``retval`` are read-write.
  */
 struct hid_bpf_ctx {
-	const struct hid_device *hid;
+	struct hid_device *hid;
 	__u32 allocated_size;
 	union {
 		__s32 retval;