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From:   Kalle Valo <kvalo@kernel.org>
To:     <Ajay.Kathat@microchip.com>
Cc:     <linux-wireless@vger.kernel.org>, <Claudiu.Beznea@microchip.com>,
        <Sripad.Balwadgi@microchip.com>, <stable@vger.kernel.org>,
        <mwalle@kernel.org>
Subject: Re: [PATCH v2] wifi: wilc1000: fix kernel oops during interface down during background scan
References: <20230505232902.22651-1-ajay.kathat@microchip.com>
Date:   Sat, 06 May 2023 08:57:40 +0300
In-Reply-To: <20230505232902.22651-1-ajay.kathat@microchip.com> (Ajay Kathat's
        message of "Fri, 5 May 2023 23:42:51 +0000")
Message-ID: <87jzxmngrv.fsf@kernel.org>
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<Ajay.Kathat@microchip.com> writes:

> Fix for kernel crash observed with following test procedure:
>   while true;
>     do ifconfig wlan0 up;
>     iw dev wlan0 scan &
>     ifconfig wlan0 down;
>   done
>
> During the above test procedure, the scan results are received from firmware
> for 'iw scan' command gets queued even when the interface is going down. It
> was causing the kernel oops when dereferencing the freed pointers.
>
> For synchronization, 'mac_close()' calls flush_workqueue() to block its
> execution till all pending work is completed. Afterwards 'wilc->close' flag
> which is set before the flush_workqueue() should avoid adding new work.
> Added 'wilc->close' check in wilc_handle_isr() which is common for
> SPI/SDIO bus to ignore the interrupts from firmware that inturns adds the
> work since the interface is getting closed.
>
> Also, removed isr_uh_routine() as it's not necessary after 'wl->close' check
> is added in wilc_handle_isr(). So now the default primary handler would be
> used for threaded IRQ.
>
> Cc: stable@vger.kernel.org
> Reported-by: Michael Walle <mwalle@kernel.org>
> Link: https://lore.kernel.org/linux-wireless/20221024135407.7udo3dwl3mqyv2yj@0002.3ffe.de/
> Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
> ---
>  changes since v1:
>   - updated commit description and included 'Link:' tag
>   - use atomic_t type for 'close' variable
>   - set close state after clearing ongoing scan operation
>   - make use of default primary handler for threaded_irq
>   - avoid false failure debug message during mac_close

Like I said in v1, atomic_t with only values 0 and 1 does not really
make sense.

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