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Message-ID: <9a7514ab-4c01-6abf-68e2-5945d9415867@linaro.org>
Date:   Mon, 16 May 2022 08:15:22 +0200
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Subject: Re: [PATCH net] NFC: nci: fix sleep in atomic context bugs caused by
 nci_skb_alloc
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To:     Duoming Zhou <duoming@zju.edu.cn>, netdev@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, davem@davemloft.net,
        edumazet@google.com, kuba@kernel.org, pabeni@redhat.com,
        gregkh@linuxfoundation.org, alexander.deucher@amd.com,
        broonie@kernel.org
References: <20220513133355.113222-1-duoming@zju.edu.cn>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <20220513133355.113222-1-duoming@zju.edu.cn>
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On 13/05/2022 15:33, Duoming Zhou wrote:
> There are sleep in atomic context bugs when the request to secure
> element of st-nci is timeout. The root cause is that nci_skb_alloc
> with GFP_KERNEL parameter is called in st_nci_se_wt_timeout which is
> a timer handler. The call paths that could trigger bugs are shown below:
> 
>     (interrupt context 1)
> st_nci_se_wt_timeout
>   nci_hci_send_event
>     nci_hci_send_data
>       nci_skb_alloc(..., GFP_KERNEL) //may sleep
> 
>    (interrupt context 2)
> st_nci_se_wt_timeout
>   nci_hci_send_event
>     nci_hci_send_data
>       nci_send_data
>         nci_queue_tx_data_frags
>           nci_skb_alloc(..., GFP_KERNEL) //may sleep
> 
> This patch changes allocation mode of nci_skb_alloc from GFP_KERNEL to
> GFP_ATOMIC in order to prevent atomic context sleeping. The GFP_ATOMIC
> flag makes memory allocation operation could be used in atomic context.
> 
> Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation ")
> Fixes: 11f54f228643 ("NFC: nci: Add HCI over NCI protocol support")
> Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>


Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>


Best regards,
Krzysztof