Re: [PATCH 1/2] wifi: mac80211: Update skb's NULL key in ieee80211_tx_h_select_key()

Johannes Berg
2025-03-24T12:17:11Z

On Fri, 2025-03-14 at 12:04 +0100, Remi Pommarel wrote:
> The ieee80211 skb control block key (set when skb was queued) could have
> been removed before ieee80211_tx_dequeue() call. ieee80211_tx_dequeue()
> already called ieee80211_tx_h_select_key() to get the current key, but
> the latter do not update the key in skb control block in case it is
> NULL. Because some drivers actually use this key in their TX callbacks
> (e.g. ath1{1,2}k_mac_op_tx()) this could lead to the use after free
> below:
>
> BUG: KASAN: slab-use-after-free in ath11k_mac_op_tx+0x590/0x61c
> Read of size 4 at addr ffffff803083c248 by task kworker/u16:4/1440

Maybe should have a Fixes: tag?

And please also tag the subject "[PATCH wireless NN/MM]".

> +++ b/net/mac80211/tx.c
> @@ -668,6 +668,12 @@ ieee80211_tx_h_select_key(struct ieee80211_tx_data *tx)
> } else if (ieee80211_is_data_present(hdr->frame_control) && tx->sta &&
> test_sta_flag(tx->sta, WLAN_STA_USES_ENCRYPTION)) {
> return TX_DROP;
> + } else {
> + /* Clear SKB CB key reference, ieee80211_tx_h_select_key()
> + * could have been called to update key info after its removal
> + * (e.g. by ieee80211_tx_dequeue()).
> + */
> + info->control.hw_key = NULL;
> }

I'm not sure this looks like the right place - should probably be done
around line 3897 before the call:

/*
* The key can be removed while the packet was queued, so need to call
* this here to get the current key.
*/
r = ieee80211_tx_h_select_key(&tx);

I'd think?

johannes