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Message-ID: <5eebd441-ded0-3668-f592-05bdeef920b1@linaro.org>
Date:   Wed, 4 May 2022 08:43:18 +0200
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Subject: Re: [PATCH net] NFC: netlink: fix sleep in atomic bug when firmware
 download timeout
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To:     Duoming Zhou <duoming@zju.edu.cn>, linux-kernel@vger.kernel.org
Cc:     davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
        pabeni@redhat.com, netdev@vger.kernel.org
References: <20220504055847.38026-1-duoming@zju.edu.cn>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <20220504055847.38026-1-duoming@zju.edu.cn>
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Precedence: bulk

On 04/05/2022 07:58, Duoming Zhou wrote:
> There are sleep in atomic bug that could cause kernel panic during
> firmware download process. The root cause is that nlmsg_new with
> GFP_KERNEL parameter is called in fw_dnld_timeout which is a timer
> handler. The call trace is shown below:
> 
> BUG: sleeping function called from invalid context at include/linux/sched/mm.h:265
> Call Trace:
> kmem_cache_alloc_node
> __alloc_skb
> nfc_genl_fw_download_done
> call_timer_fn
> __run_timers.part.0
> run_timer_softirq
> __do_softirq
> ...
> 
> The nlmsg_new with GFP_KERNEL parameter may sleep during memory
> allocation process, and the timer handler is run as the result of
> a "software interrupt" that should not call any other function
> that could sleep.
> 
> This patch changes allocation mode of netlink message from GFP_KERNEL
> to GFP_ATOMIC in order to prevent sleep in atomic bug. The GFP_ATOMIC
> flag makes memory allocation operation could be used in atomic context.
> 
> Fixes: 9674da8759df ("NFC: Add firmware upload netlink command")
> Fixes: 9ea7187c53f6 ("NFC: netlink: Rename CMD_FW_UPLOAD to CMD_FW_DOWNLOAD")
> Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>


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


Best regards,
Krzysztof