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Message-ID: <6b529058-3650-72bb-7541-9fbfb8c6ad9b@broadcom.com>
Date:   Thu, 22 Dec 2022 11:59:53 +0100
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Subject: Re: [PATCH] wifi: brcmfmac: unmap dma buffer in
 brcmf_msgbuf_alloc_pktid()
To:     shaozhengchao <shaozhengchao@huawei.com>,
        Kalle Valo <kvalo@kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     netdev@vger.kernel.org, linux-wireless@vger.kernel.org,
        brcm80211-dev-list.pdl@broadcom.com,
        SHA-cyfmac-dev-list@infineon.com, davem@davemloft.net,
        edumazet@google.com, kuba@kernel.org, pabeni@redhat.com,
        aspriel@gmail.com, franky.lin@broadcom.com,
        hante.meuleman@broadcom.com, wright.feng@cypress.com,
        chi-hsien.lin@cypress.com, a.fatoum@pengutronix.de,
        alsi@bang-olufsen.dk, pieterpg@broadcom.com, dekim@broadcom.com,
        linville@tuxdriver.com, weiyongjun1@huawei.com,
        yuehaibing@huawei.com
References: <20221207013114.1748936-1-shaozhengchao@huawei.com>
 <167164758059.5196.17408082243455710150.kvalo@kernel.org>
 <Y6QJWPDXglDjUP9p@linutronix.de> <87cz8bkeqp.fsf@kernel.org>
 <47236b24-6b47-b03a-c7b8-c46ea07cac6f@huawei.com>
From:   Arend van Spriel <arend.vanspriel@broadcom.com>
In-Reply-To: <47236b24-6b47-b03a-c7b8-c46ea07cac6f@huawei.com>
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On 12/22/2022 9:52 AM, shaozhengchao wrote:
> 
> 
> On 2022/12/22 16:46, Kalle Valo wrote:
>> Sebastian Andrzej Siewior <bigeasy@linutronix.de> writes:
>>
>>> On 2022-12-21 18:33:06 [+0000], Kalle Valo wrote:
>>>> Zhengchao Shao <shaozhengchao@huawei.com> wrote:
>>>>
>>>>> After the DMA buffer is mapped to a physical address, address is 
>>>>> stored
>>>>> in pktids in brcmf_msgbuf_alloc_pktid(). Then, pktids is parsed in
>>>>> brcmf_msgbuf_get_pktid()/brcmf_msgbuf_release_array() to obtain 
>>>>> physaddr
>>>>> and later unmap the DMA buffer. But when count is always equal to
>>>>> pktids->array_size, physaddr isn't stored in pktids and the DMA buffer
>>>>> will not be unmapped anyway.
>>>>>
>>>>> Fixes: 9a1bb60250d2 ("brcmfmac: Adding msgbuf protocol.")
>>>>> Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
>>>>
>>>> Can someone review this?
>>>
>>> After looking at the code, that skb is mapped but not inserted into the
>>> ringbuffer in this condition. The function returns with an error and the
>>> caller will free that skb (or add to a list for later). Either way the
>>> skb remains mapped which is wrong. The unmap here is the right thing to
>>> do.
>>>
>>> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>>
>> Thanks for the review, very much appreciated.
>>
> 
> Thank you very much.

Good catch. Has this path been observed or is this found by inspecting 
the code? Just curious.

Regards,
Arend

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