Re: [PATCH] wifi: brcmfmac: unmap dma buffer in brcmf_msgbuf_alloc_pktid()

[Arend van Spriel <arend.vanspriel@broadcom.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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