[PATCH v5] wifi: mt76: Fix NULL Dereference caused by mt76_connac_get_he_phy_cap()

[Zichen Xie]

IMHO, using operator "&" for a NULL dereferenced pointer won't cause a
crash. 've' will only be assigned to a invalid address.

So we can put off the NULL check after
'const struct ieee80211_he_cap_elem *ve = &vc->he_cap_elem;'

Best Regards,
Zichen

On Mon, Oct 7, 2024 at 9:23 AM Matthias Brugger <matthias.bgg at gmail.com> wrote:
>
>
>
> On 03/10/2024 20:09, Gax-c wrote:
> > From: Zichen Xie <zichenxie0106 at gmail.com>
> >
> > mt76_connac_get_he_phy_cap() may return a NULL pointer,
> > leading to NULL Pointer Dereference.
> > Add a NULL check for the returned pointer.
> >
> > Fixes: a5c372f77aa7 ("wifi: mt76: mt7925: extend mt7925_mcu_bss_he_tlv for per-link BSS")
> > Fixes: e6d557a78b60 ("mt76: mt7915: rely on mt76_connac_get_phy utilities")
> > Fixes: 98686cd21624 ("wifi: mt76: mt7996: add driver for MediaTek Wi-Fi 7 (802.11be) devices")
> > Signed-off-by: Zichen Xie <zichenxie0106 at gmail.com>
> > ---
> >   drivers/net/wireless/mediatek/mt76/mt7915/mcu.c | 5 +++++
> >   drivers/net/wireless/mediatek/mt76/mt7925/mcu.c | 2 ++
> >   drivers/net/wireless/mediatek/mt76/mt7996/mcu.c | 2 ++
> >   3 files changed, 9 insertions(+)
> >
> > diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c b/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c
> > index 87d0dd040001..762be3a37228 100644
> > --- a/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c
> > +++ b/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c
> > @@ -551,6 +551,8 @@ mt7915_mcu_bss_he_tlv(struct sk_buff *skb, struct ieee80211_vif *vif,
> >       struct tlv *tlv;
> >
> >       cap = mt76_connac_get_he_phy_cap(phy->mt76, vif);
> > +     if (!cap)
> > +             return;
> >
> >       tlv = mt76_connac_mcu_add_tlv(skb, BSS_INFO_HE_BASIC, sizeof(*he));
> >
> > @@ -1145,6 +1147,9 @@ mt7915_mcu_sta_bfer_he(struct ieee80211_sta *sta, struct ieee80211_vif *vif,
> >       u8 nss_mcs = mt7915_mcu_get_sta_nss(mcs_map);
> >       u8 snd_dim, sts;
> >
> > +     if (!vc)
> > +             return;
> > +
>
> That will already blow up at line:
>          const struct ieee80211_he_cap_elem *ve = &vc->he_cap_elem;
>
> This needs some more code changes.
>
> Regards,
> Matthias
>
> >       bf->tx_mode = MT_PHY_TYPE_HE_SU;
> >
> >       mt7915_mcu_sta_sounding_rate(bf);
> > diff --git a/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c b/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c
> > index 748ea6adbc6b..55e4cda2f20f 100644
> > --- a/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c
> > +++ b/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c
> > @@ -2508,6 +2508,8 @@ mt7925_mcu_bss_he_tlv(struct sk_buff *skb, struct ieee80211_bss_conf *link_conf,
> >       struct tlv *tlv;
> >
> >       cap = mt76_connac_get_he_phy_cap(phy->mt76, link_conf->vif);
> > +     if (!cap)
> > +             return;
> >
> >       tlv = mt76_connac_mcu_add_tlv(skb, UNI_BSS_INFO_HE_BASIC, sizeof(*he));
> >
> > diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c b/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c
> > index 6c445a9dbc03..55bb2d0e67e5 100644
> > --- a/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c
> > +++ b/drivers/net/wireless/mediatek/mt76/mt7996/mcu.c
> > @@ -798,6 +798,8 @@ mt7996_mcu_bss_he_tlv(struct sk_buff *skb, struct ieee80211_vif *vif,
> >       struct tlv *tlv;
> >
> >       cap = mt76_connac_get_he_phy_cap(phy->mt76, vif);
> > +     if (!cap)
> > +             return;
> >
> >       tlv = mt7996_mcu_add_uni_tlv(skb, UNI_BSS_INFO_HE_BASIC, sizeof(*he));
> >