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

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Date:   Thu, 22 Dec 2022 10:46:22 +0200
From:   Kalle Valo <kvalo@...nel.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Zhengchao Shao <shaozhengchao@...wei.com>, 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()

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.

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