wifi: mac80211: fix per-STA profile length in cross-link CSA parsing

ieee80211_mgd_check_cross_link_csa() starts parsing elements after the
fixed per-STA profile header and the STA Info field, but subtracts only
the STA Info length from the profile length. As a result,
ieee802_11_parse_elems() is given sizeof(*prof) == 3 bytes beyond the
current profile's element area, and data following the profile may be
interpreted as belonging to it.

Subtract the fixed profile header as well. The preceding
ieee80211_mle_basic_sta_prof_size_ok() check guarantees that the
corrected calculation cannot underflow, and
ieee80211_rx_uhr_link_reconfig_req() uses the same calculation.

The call site currently states that cross-link CSA parsing has no effect
because the broader parsing is still incorrect. This patch does not
address that broader problem; it only makes the per-STA profile parser
stop at the end of that profile. No production allocation over-read or
user-visible failure has been demonstrated.

Fixes: 7ef8f6821d ("wifi: mac80211: mlme: handle cross-link CSA")
Assisted-by: Codex:gpt-5.6-sol
Assisted-by: Kimi:K3
Signed-off-by: Zhao Li <enderaoelyther@gmail.com>
Link: https://patch.msgid.link/20260728111326.63087-1-enderaoelyther@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mlme.c

@@ -8027,7 +8027,7 @@ ieee80211_mgd_check_cross_link_csa(struct ieee80211_sub_if_data *sdata,
 		prof = (void *)sta_profiles[link_id];
 		prof_elems = ieee802_11_parse_elems(prof->variable +
 						    (prof->sta_info_len - 1),
-						    len -
+						    len - sizeof(*prof) -
 						    (prof->sta_info_len - 1),
 						    IEEE80211_FTYPE_MGMT |
 						    IEEE80211_STYPE_BEACON,