CVE-2026-64255

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

wifi: iwlwifi: mld: validate sta_mask before ffs() in BA session handlers

Three BA session handlers use ffs(ba_data->sta_mask) - 1 to derive a
station ID without checking that sta_mask is non-zero. When sta_mask is
zero, ffs() returns 0 and the subtraction wraps to 0xFFFFFFFF, causing
an out-of-bounds access on fw_id_to_link_sta[].

Add WARN_ON_ONCE(!ba_data->sta_mask) guards before each ffs() call,
consistent with the existing check in iwl_mld_ampdu_rx_start().