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

[Matthias Brugger <matthias.bgg@gmail.com>]

On 07/10/2024 17:36, Zichen Xie wrote:
> IMHO, using operator "&" for a NULL dereferenced pointer won't cause a
> crash. 've' will only be assigned to a invalid address.
> 

Please don't top post.

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

You are right, nevertheless for better code readability I'd still advise to 
change the code so that vc is checked for NULL before any use of struct vc.

Regards,
Matthias

> Best Regards,
> Zichen
> 
> On Mon, Oct 7, 2024 at 9:23 AM Matthias Brugger <matthias.bgg@gmail.com> wrote:
>>
>>
>>
>> On 03/10/2024 20:09, Gax-c wrote:
>>> From: Zichen Xie <zichenxie0106@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@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));
>>>