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

Arend van Spriel <arend.vanspriel@xxxxxxxxxxxx> · Thu, 22 Dec 2022 12:37:04 +0100

On 12/22/2022 12:35 PM, shaozhengchao wrote:

-----Original Message-----
From: Arend van Spriel [mailto:arend.vanspriel@xxxxxxxxxxxx]
Sent: Thursday, December 22, 2022 7:00 PM
To: shaozhengchao <shaozhengchao@xxxxxxxxxx>; Kalle Valo <kvalo@xxxxxxxxxx>; Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx; linux-wireless@xxxxxxxxxxxxxxx; brcm80211-dev-list.pdl@xxxxxxxxxxxx; SHA-cyfmac-dev-list@xxxxxxxxxxxx; davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx; aspriel@xxxxxxxxx; franky.lin@xxxxxxxxxxxx; hante.meuleman@xxxxxxxxxxxx; wright.feng@xxxxxxxxxxx; chi-hsien.lin@xxxxxxxxxxx; a.fatoum@xxxxxxxxxxxxxx; alsi@xxxxxxxxxxxxxxx; pieterpg@xxxxxxxxxxxx; dekim@xxxxxxxxxxxx; linville@xxxxxxxxxxxxx; weiyongjun (A) <weiyongjun1@xxxxxxxxxx>; yuehaibing <yuehaibing@xxxxxxxxxx>
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@xxxxxxxxxxxxx> writes:

On 2022-12-21 18:33:06 [+0000], Kalle Valo wrote:
Zhengchao Shao <shaozhengchao@xxxxxxxxxx> 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@xxxxxxxxxx>

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@xxxxxxxxxxxxx>

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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