patch 46/47 causes NULL pointer deref on mt7921

[Bert Karwatzki]

Am Mittwoch, dem 31.07.2024 um 11:51 +0300 schrieb Kalle Valo:
> Bert Karwatzki <spasswolf at web.de> writes:
>
> > Am Mittwoch, dem 17.07.2024 um 17:25 +0200 schrieb Felix Fietkau:
> >
> > > On 17.07.24 16:38, Bert Karwatzki wrote:
> > >
> > > > So mvif->phy can be NULL at the start of mt7921_ipv6_addr_change. The early
> > > > return in that case avoids the NULL pointer and mvif->phy has its usual value
> > > > again on the next call to mt7921_ipv6_addr_change so Wifi is working again. I
> > > > don't know how this could happen but perhaps you have an idea.
> > >
> > > This change should fix it: https://nbd.name/p/0747f54f
> > > Please test.
> >
> > The BUG is still present in linux-6.11-rc1.
>
> I'm not sure what's the status with this. There's one mt76 patch going
> to v6.11-rc2:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/wireless/wireless.git/commit/?id=6557a28f3e3a54cff4f0dcdd1dfa649b26557ab3
>
> But that looks to be a fix for a different problem, right? Felix, are
> you planning to submit that 0747f54f as a proper patch? I could then
> take it to wireless tree.
>
The Bug is still present in linux-6.11-rc2 and linux-next-20240806. Also the
mvif->phy NULL check in the original patch is not neccessary (and feels a little
out of place as mvif->phy is not needed anymore). This patch is sufficient to
fix the NULL pointer dereference:
diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/main.c
b/drivers/net/wireless/mediatek/mt76/mt7921/main.c
index 1bab93d049df..23b228804289 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/main.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/main.c
@@ -1183,7 +1183,7 @@ static void mt7921_ipv6_addr_change(struct ieee80211_hw
*hw,
                                    struct inet6_dev *idev)
 {
        struct mt792x_vif *mvif = (struct mt792x_vif *)vif->drv_priv;
-       struct mt792x_dev *dev = mvif->phy->dev;
+       struct mt792x_dev *dev = mt792x_hw_dev(hw);
        struct inet6_ifaddr *ifa;
        struct in6_addr ns_addrs[IEEE80211_BSS_ARP_ADDR_LIST_LEN];
        struct sk_buff *skb;

Bert Karwatzki