linux-kernel - Re: [PATCH v2 2/8] bus: mhi: core: Add range check for channel id received in event ring

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Date:   Wed, 29 Apr 2020 10:29:33 -0700
From:   Hemant Kumar <hemantk@...eaurora.org>
To:     Jeffrey Hugo <jhugo@...eaurora.org>,
        Bhaumik Bhatt <bbhatt@...eaurora.org>, mani@...nel.org
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/8] bus: mhi: core: Add range check for channel id
 received in event ring

Hi Jeff

On 4/28/20 7:44 AM, Jeffrey Hugo wrote:
> On 4/27/2020 8:59 PM, Bhaumik Bhatt wrote:
>> From: Hemant Kumar <hemantk@...eaurora.org>
>>
>> MHI data completion handler function reads channel id from event
>> ring element. Value is under the control of MHI devices and can be
>> any value between 0 and 255. In order to prevent out of bound access
>> add a bound check against the max channel supported by controller
>> and skip processing of that event ring element.
>>
>> Signed-off-by: Hemant Kumar <hemantk@...eaurora.org>
>> Signed-off-by: Bhaumik Bhatt <bbhatt@...eaurora.org>
>> ---
>>   drivers/bus/mhi/core/main.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
>> index 23154f1..1ccd4cc 100644
>> --- a/drivers/bus/mhi/core/main.c
>> +++ b/drivers/bus/mhi/core/main.c
>> @@ -827,6 +827,9 @@ int mhi_process_data_event_ring(struct 
>> mhi_controller *mhi_cntrl,
>>           enum mhi_pkt_type type = MHI_TRE_GET_EV_TYPE(local_rp);
>>           chan = MHI_TRE_GET_EV_CHID(local_rp);
>> +        if (WARN_ON(chan >= mhi_cntrl->max_chan))
>> +            goto next_event;
>> +
>>           mhi_chan = &mhi_cntrl->mhi_chan[chan];
>>           if (likely(type == MHI_PKT_TYPE_TX_EVENT)) {
>> @@ -837,6 +840,7 @@ int mhi_process_data_event_ring(struct 
>> mhi_controller *mhi_cntrl,
>>               event_quota--;
>>           }
>> +next_event:
>>           mhi_recycle_ev_ring_element(mhi_cntrl, ev_ring);
>>           local_rp = ev_ring->rp;
>>           dev_rp = mhi_to_virtual(ev_ring, er_ctxt->rp);
>>
> 
> It looks like the same issue exists in mhi_process_ctrl_ev_ring(), and 
> thus some form of this solution needs to be applied there as well. Would 
> you please fix that too?
> 
As discussed with you off line, spec allows to have just event ring to 
be used for both data and control. Updating this in V3.

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