[bug report] wifi: mt76: Check link_conf pointer in mt76_connac_mcu_sta_basic_tlv()

[Lorenzo Bianconi]

> Hello Shayne Chen,
> 
> This is a semi-automatic email about new static checker warnings.
> 
> Commit 9890624c1b39 ("wifi: mt76: Check link_conf pointer in
> mt76_connac_mcu_sta_basic_tlv()") from Mar 11, 2025, leads to the
> following Smatch complaint:
> 
>     drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c:394 mt76_connac_mcu_sta_basic_tlv()
>     warn: variable dereferenced before check 'link_conf' (see line 376)
> 
> drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
>    375	{
>    376		struct ieee80211_vif *vif = link_conf->vif;
>                                             ^^^^^^^^^^^^^^

Reviewing the codebase, it seems to me it is safe to revert 9890624c1b39 since
link_conf is always not NULL running mt76_connac_mcu_sta_basic_tlv().
@Shayne Chen: agree?

Regards,
Lorenzo

> Dereferenced.
> 
>    377		struct sta_rec_basic *basic;
>    378		struct tlv *tlv;
>    379		int conn_type;
>    380	
>    381		tlv = mt76_connac_mcu_add_tlv(skb, STA_REC_BASIC, sizeof(*basic));
>    382	
>    383		basic = (struct sta_rec_basic *)tlv;
>    384		basic->extra_info = cpu_to_le16(EXTRA_INFO_VER);
>    385	
>    386		if (newly && conn_state != CONN_STATE_DISCONNECT)
>    387			basic->extra_info |= cpu_to_le16(EXTRA_INFO_NEW);
>    388		basic->conn_state = conn_state;
>    389	
>    390		if (!link_sta) {
>    391			basic->conn_type = cpu_to_le32(CONNECTION_INFRA_BC);
>    392	
>    393			if (vif->type == NL80211_IFTYPE_STATION &&
>    394			    link_conf && !is_zero_ether_addr(link_conf->bssid)) {
>                             ^^^^^^^^^
> The patch adds a NULL dereference but it's too late.
> 
>    395				memcpy(basic->peer_addr, link_conf->bssid, ETH_ALEN);
>    396				basic->aid = cpu_to_le16(vif->cfg.aid);
> 
> regards,
> dan carpenter
> 
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