Re: [bug report] mt76: mt76_connac: create mcu library

[Lorenzo Bianconi <lorenzo@kernel.org>]

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> Hello Lorenzo Bianconi,

Hi Dan,

> 
> The patch d0e274af2f2e: "mt76: mt76_connac: create mcu library" from
> Jan 26, 2021, leads to the following static checker warning:
> 
> 	drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c:837 mt76_connac_mcu_add_sta_cmd()
> 	error: 'wtbl_hdr' dereferencing possible ERR_PTR()
> 
> drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
>    810  int mt76_connac_mcu_add_sta_cmd(struct mt76_phy *phy,
>    811                                  struct ieee80211_vif *vif,
>    812                                  struct ieee80211_sta *sta,
>    813                                  struct mt76_wcid *wcid,
>    814                                  bool enable, int cmd)
>    815  {
>    816          struct mt76_vif *mvif = (struct mt76_vif *)vif->drv_priv;
>    817          struct mt76_dev *dev = phy->dev;
>    818          struct wtbl_req_hdr *wtbl_hdr;
>    819          struct tlv *sta_wtbl;
>    820          struct sk_buff *skb;
>    821  
>    822          skb = mt76_connac_mcu_alloc_sta_req(dev, mvif, wcid);
>    823          if (IS_ERR(skb))
>    824                  return PTR_ERR(skb);
>    825  
>    826          mt76_connac_mcu_sta_basic_tlv(skb, vif, sta, enable);
>    827          if (enable && sta)
>    828                  mt76_connac_mcu_sta_tlv(phy, skb, sta, vif);
>    829  
>    830          sta_wtbl = mt76_connac_mcu_add_tlv(skb, STA_REC_WTBL,
>    831                                             sizeof(struct tlv));
>    832  
>    833          wtbl_hdr = mt76_connac_mcu_alloc_wtbl_req(dev, wcid,
>    834                                                    WTBL_RESET_AND_SET,
>    835                                                    sta_wtbl, &skb);
> 
> if (IS_ERR(wtbl_hdr)) {
> 	do some cleanup?
> 	return PTR_ERR(wtbl_hdr);
> }

I think this is a false positive since reviewing
mt76_connac_mcu_alloc_wtbl_req(), it can return ERR_PTR(-ENOMEM) only if nskb
is NULL and it is not the case.

Regards,
Lorenzo

> 
>    836          if (enable) {
>    837                  mt76_connac_mcu_wtbl_generic_tlv(dev, skb, vif, sta, sta_wtbl,
>    838                                                   wtbl_hdr);
>    839                  if (sta)
>    840                          mt76_connac_mcu_wtbl_ht_tlv(dev, skb, sta, sta_wtbl,
>    841                                                      wtbl_hdr);
>    842          }
>    843  
>    844          return mt76_mcu_skb_send_msg(dev, skb, cmd, true);
>    845  }
> 
> regards,
> dan carpenter

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