linux-kernel - Re: patch 46/47 causes NULL pointer deref on mt7921

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Message-ID: <87y15211ci.fsf@kernel.org>
Date: Mon, 12 Aug 2024 13:29:01 +0300
From: Kalle Valo <kvalo@...nel.org>
To: Bert Karwatzki <spasswolf@....de>
Cc: Felix Fietkau <nbd@....name>,  Sean Wang <sean.wang@...nel.org>,
  deren.wu@...iatek.com,  linux-mediatek@...ts.infradead.org,
  linux-wireless@...r.kernel.org,  lorenzo.bianconi@...hat.com,
  mingyen.hsieh@...iatek.com,  sean.wang@...iatek.com,
  linux-kernel@...r.kernel.org
Subject: Re: patch 46/47 causes NULL pointer deref on mt7921

Bert Karwatzki <spasswolf@....de> writes:

> Am Dienstag, dem 06.08.2024 um 13:22 +0200 schrieb Bert Karwatzki:
>> Am Mittwoch, dem 31.07.2024 um 11:51 +0300 schrieb Kalle Valo:
>> > Bert Karwatzki <spasswolf@....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
>
> This error is still present in v6.11-rc3.

Bert, can you send your fix as a proper patch? More information in the
wiki below and please mark it for wireless tree.

-- 
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches