netdev - Re: [PATCH net-next] net: ethernet: mtk_wed: fix possible deadlock if mtk_wed_wo

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Date:   Sun, 4 Dec 2022 15:06:54 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     netdev@...r.kernel.org, nbd@....name, john@...ozen.org,
        sean.wang@...iatek.com, Mark-MC.Lee@...iatek.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, matthias.bgg@...il.com,
        linux-mediatek@...ts.infradead.org, lorenzo.bianconi@...hat.com
Subject: Re: [PATCH net-next] net: ethernet: mtk_wed: fix possible deadlock
 if mtk_wed_wo_init fails

On Fri, Dec 02, 2022 at 06:36:33PM +0100, Lorenzo Bianconi wrote:
> Introduce __mtk_wed_detach() in order to avoid a possible deadlock in
> mtk_wed_attach routine if mtk_wed_wo_init fails.
> 
> Fixes: 4c5de09eb0d0 ("net: ethernet: mtk_wed: add configure wed wo support")
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---
>  drivers/net/ethernet/mediatek/mtk_wed.c     | 24 ++++++++++++++-------
>  drivers/net/ethernet/mediatek/mtk_wed_mcu.c | 10 ++++++---
>  drivers/net/ethernet/mediatek/mtk_wed_wo.c  |  3 +++
>  3 files changed, 26 insertions(+), 11 deletions(-)

<...>

> diff --git a/drivers/net/ethernet/mediatek/mtk_wed_mcu.c b/drivers/net/ethernet/mediatek/mtk_wed_mcu.c
> index f9539e6233c9..b084009a32f9 100644
> --- a/drivers/net/ethernet/mediatek/mtk_wed_mcu.c
> +++ b/drivers/net/ethernet/mediatek/mtk_wed_mcu.c
> @@ -176,6 +176,9 @@ int mtk_wed_mcu_send_msg(struct mtk_wed_wo *wo, int id, int cmd,
>  	u16 seq;
>  	int ret;
>  
> +	if (!wo)
> +		return -ENODEV;

<...>

>  static void
>  mtk_wed_wo_hw_deinit(struct mtk_wed_wo *wo)
>  {
> +	if (!wo)
> +		return;

How are these changes related to the written in deadlock?
How is it possible to get internal mtk functions without valid wo?

Thanks

> +
>  	/* disable interrupts */
>  	mtk_wed_wo_set_isr(wo, 0);
>  
> -- 
> 2.38.1
>