CVE-2026-74488: wifi: mwifiex: use the subframe length when parsing A-MSDU TDLS frames

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

wifi: mwifiex: use the subframe length when parsing A-MSDU TDLS frames

mwifiex11ndispatchamsdupkt() splits an A-MSDU with ieee80211amsduto8023s() and walks the resulting subframes. For each subframe it passes the subframe data pointer to mwifiexprocesstdlsactionframe(), but pairs it with skb->len, the length of the A-MSDU parent, instead of rxskb->len:

rxskb = skbdequeue(&list); rxhdr = (struct rxpackethdr )rxskb->data; if (ISSUPPTDLSENABLED(priv->adapter->fwcapinfo) && ntohs(rxhdr->eth803hdr.hproto) == ETHPTDLS) { mwifiexprocesstdlsactionframe(priv, (u8 )rxhdr, skb->len); }

The parent is not a valid description of that buffer, and may not be valid memory at all. ieee80211amsduto8023s() ends with

if (!reuseskb) devkfreeskb(skb);

and it only sets reuseskb when the parent is linear, is not a headfrag, and is being consumed as the last subframe. So when the parent does not qualify for reuse it has already been freed, and the read of skb->len is a use-after-free. When it is reused, skb->len is the length of the last subframe, applied to every earlier subframe, which over-states the buffer whenever an earlier subframe is shorter.

The callee cannot absorb a wrong length, because it derives its own ceiling from the value it is given. Each frame type computes

ieslen = len - sizeof(struct ethhdr) - TDLSFIXLEN;

and the element walk is then bounded entirely against that ceiling,

for (end = pos + ieslen; pos + 1 < end; pos += 2 + pos[1]) { u8 ielen = pos[1];

if (pos + 2 + ielen > end) break;

so a too-large len moves end past the end of the subframe and the walk reads and copies beyond it. The A-MSDU layout is chosen by the sender, which makes the difference between the last subframe and a shorter earlier one remotely selectable. Reaching this requires TDLS support in firmware and the TDLS ethertype on the subframe.

The other caller, mwifiexprocessrxpacket(), is correct: it passes a pointer and a length that describe the same region of the RX buffer.

Pass rxskb->len, the length of the subframe actually being parsed.