Bluetooth: eir: Fix OOB read in eir_get_service_data()

Summary

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: eir: Fix OOB read in eir_get_service_data() eir_get_service_data() walks the advertising data for a Service Data field with a matching UUID. On a mismatch it advances: eir += dlen; eir_len -= dlen; eir_get_data() reports dlen as the field's data length, but the field spans dlen + 2 bytes once its length and type bytes count, and more when non-Service-Data fields were skipped to reach it. The pointer lands correctly on the next field. eir_len does not, and the shortfall compounds across fields until eir_get_data() reads the length and type bytes of a "field" past the end of the buffer. For an ISO broadcast sink that buffer is hcon->le_per_adv_data[], filled from the periodic advertising reports of a remote broadcaster. A PA payload packed with mismatching Service Data fields walks off the array into the rest of struct hci_conn. A drifted field that matches the BAA UUID puts those bytes in iso_pi(sk)->base, where user space reads them back with getsockopt(BT_ISO_BASE). Recompute eir_len from the end of the buffer each iteration.