CVE-2026-98810: wifi: mac80211: fix slab-out-of-bounds read in ieee80211_monitor_select_queue()

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

wifi: mac80211: fix slab-out-of-bounds read in ieee80211monitorselectqueue()

ieee80211monitorselectqueue() validates the skb length using skb->len before dereferencing pointers into skb->data to access the 802.11 header. However, skb->len includes data in both the linear head buffer and non-linear fragments/pages. When AFPACKET sends a packet large enough to become non-linear, the 802.11 header at skb->data + lenrthdr may extend past the linear head buffer even though skb->len appears sufficient.

This leads to a slab-out-of-bounds read when accessing hdr->framecontrol, as the kernel reads beyond the allocated skb head buffer:

BUG: KASAN: slab-out-of-bounds in ieee80211monitorselectqueue+0x1ed/0x220

syzbot has hit the same issues.

Fix this by checking skbheadlen(skb) (which gives the length of the linear data region) instead of skb->len before dereferencing skb->data pointers. This ensures the required bytes are actually present in the linear portion of the skb.

Apply the same fix to ieee80211validateradiotaplen() which has the same class of bug: it uses skb->len to validate accesses to skb->data, and to the corresponding checks in ieee80211monitorstartxmit(): for drivers advertising NETIFFSG the skb is not linearized before ndostartxmit, so the 802.11 header can be read past the linear buffer there as well.