linux-kernel - Re: [PATCH v3 3/4] bus: mhi: host: Avoid processing buffer and event of a disable channel

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Message-ID: <72bb93a5-29a7-4608-b787-18a982df38ba@quicinc.com>
Date:   Tue, 14 Nov 2023 14:17:11 +0800
From:   Qiang Yu <quic_qianyu@...cinc.com>
To:     Manivannan Sadhasivam <mani@...nel.org>
CC:     <quic_jhugo@...cinc.com>, <mhi@...ts.linux.dev>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <quic_cang@...cinc.com>, <quic_mrana@...cinc.com>
Subject: Re: [PATCH v3 3/4] bus: mhi: host: Avoid processing buffer and event
 of a disable channel


On 11/10/2023 11:38 AM, Qiang Yu wrote:
>
> On 11/10/2023 12:32 AM, Manivannan Sadhasivam wrote:
>> On Tue, Nov 07, 2023 at 03:16:04PM +0800, Qiang Yu wrote:
>>> Ckeck mhi channel state after getting chan->lock to ensure that we only
>>> queue buffer to an enabled channel and process event of an enabled 
>>> channel.
>>>
>> This commit message doesn't give proper explanation on how the 
>> channel can go to
>> disabled state in between parse_xfer_event() and mhi_gen_tre().
>>
>> - Mani
>
> Hi Mani. How about following commit message
>
> MHI channel state is protected by mhi_chan->lock. Hence, after core drops
> mhi_chan->lock during processing xfer event, it can not prevent channel
> state being changed if client closes channel or driver is removed at this
> time. So let's check mhi channel state after getting chan->lock again 
> to avoid
> queuing buffer to a disabled channel in xfer callback and stop processing
> event of the disabled channel.
Hi Mani, Have updated this commit message in V4 patch, hope get your 
comments.
>
>>> Signed-off-by: Qiang Yu <quic_qianyu@...cinc.com>
>>> ---
>>>   drivers/bus/mhi/host/main.c | 4 ++++
>>>   1 file changed, 4 insertions(+)
>>>
>>> diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
>>> index a236dc2..b137d54 100644
>>> --- a/drivers/bus/mhi/host/main.c
>>> +++ b/drivers/bus/mhi/host/main.c
>>> @@ -672,6 +672,8 @@ static int parse_xfer_event(struct 
>>> mhi_controller *mhi_cntrl,
>>>               }
>>>                 read_lock_bh(&mhi_chan->lock);
>>> +            if (mhi_chan->ch_state != MHI_CH_STATE_ENABLED)
>>> +                goto end_process_tx_event;
>>>           }
>>>           break;
>>>       } /* CC_EOT */
>>> @@ -1211,6 +1213,8 @@ int mhi_gen_tre(struct mhi_controller 
>>> *mhi_cntrl, struct mhi_chan *mhi_chan,
>>>         /* Protect accesses for reading and incrementing WP */
>>>       write_lock_bh(&mhi_chan->lock);
>>> +    if (mhi_chan->ch_state != MHI_CH_STATE_ENABLED)
>>> +        return -EINVAL;
>>>         buf_ring = &mhi_chan->buf_ring;
>>>       tre_ring = &mhi_chan->tre_ring;
>>> -- 
>>> 2.7.4
>>>
>>>
>