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Date:   Thu, 22 Dec 2022 11:59:53 +0100
From:   Arend van Spriel <>
To:     shaozhengchao <>,
        Kalle Valo <>,
        Sebastian Andrzej Siewior <>
Subject: Re: [PATCH] wifi: brcmfmac: unmap dma buffer in

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


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