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Message-ID: <58d61ba6-3cd9-cfee-d6d1-2bb800853eb4@broadcom.com>
Date:   Thu, 22 Dec 2022 12:37:04 +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" <netdev@vger.kernel.org>,
        "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
        "brcm80211-dev-list.pdl@broadcom.com" 
        <brcm80211-dev-list.pdl@broadcom.com>,
        "SHA-cyfmac-dev-list@infineon.com" <SHA-cyfmac-dev-list@infineon.com>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "edumazet@google.com" <edumazet@google.com>,
        "kuba@kernel.org" <kuba@kernel.org>,
        "pabeni@redhat.com" <pabeni@redhat.com>,
        "aspriel@gmail.com" <aspriel@gmail.com>,
        "franky.lin@broadcom.com" <franky.lin@broadcom.com>,
        "hante.meuleman@broadcom.com" <hante.meuleman@broadcom.com>,
        "wright.feng@cypress.com" <wright.feng@cypress.com>,
        "chi-hsien.lin@cypress.com" <chi-hsien.lin@cypress.com>,
        "a.fatoum@pengutronix.de" <a.fatoum@pengutronix.de>,
        "alsi@bang-olufsen.dk" <alsi@bang-olufsen.dk>,
        "pieterpg@broadcom.com" <pieterpg@broadcom.com>,
        "dekim@broadcom.com" <dekim@broadcom.com>,
        "linville@tuxdriver.com" <linville@tuxdriver.com>,
        "weiyongjun (A)" <weiyongjun1@huawei.com>,
        yuehaibing <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>
 <6b529058-3650-72bb-7541-9fbfb8c6ad9b@broadcom.com>
 <fc8a7c6ac335473b901aa9815167754f@huawei.com>
From:   Arend van Spriel <arend.vanspriel@broadcom.com>
In-Reply-To: <fc8a7c6ac335473b901aa9815167754f@huawei.com>
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On 12/22/2022 12:35 PM, shaozhengchao wrote:
> 
> 
> -----Original Message-----
> From: Arend van Spriel [mailto:arend.vanspriel@broadcom.com]
> Sent: Thursday, December 22, 2022 7:00 PM
> 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; weiyongjun (A) <weiyongjun1@huawei.com>; yuehaibing <yuehaibing@huawei.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@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
> 
> Hi Arend：
> 	I review code and find the bug.


Much appreciated.

Regards,
Arend

> Zhengchao Shao

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