CVE-2026-74300: Bluetooth: hci: validate codec capability element length

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: hci: validate codec capability element length

Read Local Codec Capabilities returns a sequence of capability elements. Each element starts with a one-byte length followed by that many payload bytes.

hcireadcodeccapabilities() checks that the skb contains the length byte, but then validates only caps->len against the remaining skb length. A malformed controller response with one remaining byte and caps->len set to one passes that check even though the element needs two bytes. The parser then records a two-byte capability and copies one byte beyond the advertised response payload into the codec list.

Validate the full element size, including the length byte, before adding it to the accumulated capability length. This preserves all well-formed capability elements and drops only truncated controller responses.