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

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Message-ID: <5dfa3617-644c-42c3-0dfe-4f9f4a6d5ded@codeaurora.org>
Date:   Tue, 28 Apr 2020 08:44:15 -0600
From:   Jeffrey Hugo <jhugo@...eaurora.org>
To:     Bhaumik Bhatt <bbhatt@...eaurora.org>, mani@...nel.org
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        hemantk@...eaurora.org
Subject: Re: [PATCH v2 2/8] bus: mhi: core: Add range check for channel id
 received in event ring

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?

-- 
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.