CVE-2026-31394 — mac80211: fix crash in ieee80211_chan_bw_change for AP_VLAN stations

Affected: Linux

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

mac80211: fix crash in ieee80211_chan_bw_change for AP_VLAN stations

ieee80211_chan_bw_change() iterates all stations and accesses link->reserved.oper via sta->sdata->link[link_id]. For stations on AP_VLAN interfaces (e.g. 4addr WDS clients), sta->sdata points to the VLAN sdata, whose link never participates in chanctx reservations. This leaves link->reserved.oper zero-initialized with chan == NULL, causing a NULL pointer dereference in __ieee80211_sta_cap_rx_bw() when accessing chandef->chan->band during CSA.

Resolve the VLAN sdata to its parent AP sdata using get_bss_sdata() before accessing link data.

[also change sta->sdata in ARRAY_SIZE even if it doesn't matter]

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CVE-2026-31394 — mac80211: fix crash in ieee80211_chan_bw_change for AP_VLAN stations