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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
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To:     Kalle Valo <kvalo@kernel.org>
Cc:     Kalle Valo <quic_kvalo@quicinc.com>,
        Colin Ian King <colin.i.king@gmail.com>,
        linux-wireless@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] wifi: ath9k: Don't mark channelmap stack variable
 read-only in ath9k_mci_update_wlan_channels()
In-Reply-To: <87v8hysrzx.fsf@kernel.org>
References: <20230413214118.153781-1-toke@toke.dk> <87v8hysrzx.fsf@kernel.org>
Date:   Fri, 14 Apr 2023 12:32:05 +0200
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Kalle Valo <kvalo@kernel.org> writes:

> Toke H=C3=B8iland-J=C3=B8rgensen <toke@toke.dk> writes:
>
>> This partially reverts commit e161d4b60ae3a5356e07202e0bfedb5fad82c6aa.
>>
>> Turns out the channelmap variable is not actually read-only, it's modifi=
ed
>> through the MCI_GPM_CLR_CHANNEL_BIT() macro further down in the function,
>> so making it read-only causes page faults when that code is hit.
>>
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=3D217183
>> Fixes: e161d4b60ae3 ("wifi: ath9k: Make arrays prof_prio and channelmap =
static const")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Toke H=C3=B8iland-J=C3=B8rgensen <toke@toke.dk>
>
> I guess the casting in MCI_GPM_CLR_CHANNEL_BIT() hide this and made it
> impossible for the compiler to detect it? A perfect example why I hate
> casting :)

Yup, exactly. I was also assuming the compiler would catch it, but yay, C! =
:/

Anyway, cf the bugzilla this was a pretty bad regression for 6.2, so
would be good to move this along reasonably quickly (although I guess we
just missed the -net PR for rc7)...

-Toke