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

[shaozhengchao <shaozhengchao@huawei.com>]

-----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. 

Zhengchao Shao