netdev - Re: [PATCH] wifi: brcmfmac: unmap dma buffer in brcmf_msgbuf_alloc

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Message-ID: <6b529058-3650-72bb-7541-9fbfb8c6ad9b@broadcom.com>
Date:   Thu, 22 Dec 2022 11:59:53 +0100
From:   Arend van Spriel <arend.vanspriel@...adcom.com>
To:     shaozhengchao <shaozhengchao@...wei.com>,
        Kalle Valo <kvalo@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     netdev@...r.kernel.org, linux-wireless@...r.kernel.org,
        brcm80211-dev-list.pdl@...adcom.com,
        SHA-cyfmac-dev-list@...ineon.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        aspriel@...il.com, franky.lin@...adcom.com,
        hante.meuleman@...adcom.com, wright.feng@...ress.com,
        chi-hsien.lin@...ress.com, a.fatoum@...gutronix.de,
        alsi@...g-olufsen.dk, pieterpg@...adcom.com, dekim@...adcom.com,
        linville@...driver.com, weiyongjun1@...wei.com,
        yuehaibing@...wei.com
Subject: Re: [PATCH] wifi: brcmfmac: unmap dma buffer in
 brcmf_msgbuf_alloc_pktid()

On 12/22/2022 9:52 AM, shaozhengchao wrote:
> 
> 
> On 2022/12/22 16:46, Kalle Valo wrote:
>> Sebastian Andrzej Siewior <bigeasy@...utronix.de> writes:
>>
>>> On 2022-12-21 18:33:06 [+0000], Kalle Valo wrote:
>>>> Zhengchao Shao <shaozhengchao@...wei.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@...wei.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@...utronix.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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