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From:   Kalle Valo <kvalo@kernel.org>
To:     Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc:     Johannes Berg <johannes@sipsolutions.net>,
        Toke =?utf-8?Q?H=C3=B8ilan?= =?utf-8?Q?d-J=C3=B8rgensen?= 
        <toke@kernel.org>, Felix Fietkau <nbd@nbd.name>,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH v2] wifi: mac80211: do not abuse fq.lock in ieee80211_do_stop()
References: <9cc9b81d-75a3-3925-b612-9d0ad3cab82b@I-love.SAKURA.ne.jp>
        <165814567948.32602.9899358496438464723.kvalo@kernel.org>
        <9487e319-7ab4-995a-ddfd-67c4c701680c@I-love.SAKURA.ne.jp>
Date:   Tue, 26 Jul 2022 17:38:18 +0300
In-Reply-To: <9487e319-7ab4-995a-ddfd-67c4c701680c@I-love.SAKURA.ne.jp>
        (Tetsuo Handa's message of "Tue, 26 Jul 2022 15:55:35 +0900")
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(please don't top post, I manually fixed that)

Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> writes:

> On 2022/07/18 21:01, Kalle Valo wrote:
>> Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> wrote:
>>=20
>>> lockdep complains use of uninitialized spinlock at ieee80211_do_stop() =
[1],
>>> for commit f856373e2f31ffd3 ("wifi: mac80211: do not wake queues on a v=
if
>>> that is being stopped") guards clear_bit() using fq.lock even before
>>> fq_init() from ieee80211_txq_setup_flows() initializes this spinlock.
>>>
>>> According to discussion [2], Toke was not happy with expanding usage of
>>> fq.lock. Since __ieee80211_wake_txqs() is called under RCU read lock, we
>>> can instead use synchronize_rcu() for flushing ieee80211_wake_txqs().
>>>
>>> Link: https://syzkaller.appspot.com/bug?extid=3Deceab52db7c4b961e9d6 [1]
>>> Link: https://lkml.kernel.org/r/874k0zowh2.fsf@toke.dk [2]
>>> Reported-by: syzbot <syzbot+eceab52db7c4b961e9d6@syzkaller.appspotmail.=
com>
>>> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
>>> Fixes: f856373e2f31ffd3 ("wifi: mac80211: do not wake queues on a vif t=
hat is being stopped")
>>> Tested-by: syzbot <syzbot+eceab52db7c4b961e9d6@syzkaller.appspotmail.co=
m>
>>> Acked-by: Toke H=C3=B8iland-J=C3=B8rgensen <toke@kernel.org>
>>=20
>> Patch applied to wireless-next.git, thanks.
>>=20
>> 3598cb6e1862 wifi: mac80211: do not abuse fq.lock in ieee80211_do_stop()
>
> Since this patch fixes a regression introduced in 5.19-rc7, can this patc=
h go to 5.19-final ?
>
> syzbot is failing to test linux.git for 12 days due to this regression.
> syzbot will fail to bisect new bugs found in the upcoming merge window
> if unable to test v5.19 due to this regression.

I took this to wireless-next as I didn't think there's enough time to
get this to v5.19 (and I only heard Linus' -rc8 plans after the fact).
So this will be in v5.20-rc1 and I recommend pushing this to a v5.19
stable release.

--=20
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatc=
hes