Re: [PATCH] bus: mhi: core: Validate channel ID when processing command completions

[Manivannan Sadhasivam]

On Thu, Jun 24, 2021 at 11:09:01AM -0700, Bhaumik Bhatt wrote:
> MHI reads the channel ID from the event ring element sent by the
> device which can be any value between 0 and 255. In order to
> prevent any out of bound accesses, add a check against the maximum
> number of channels supported by the controller and those channels
> not configured yet so as to skip processing of that event ring
> element.
> 
> Fixes: 1d3173a3bae7 ("bus: mhi: core: Add support for processing events from client device")
> Signed-off-by: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>
> Reviewed-by: Hemant Kumar <hemantk@xxxxxxxxxxxxxx>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
> Reviewed-by: Jeffrey Hugo <quic_jhugo@xxxxxxxxxxx>
> Link: https://lore.kernel.org/r/1619481538-4435-1-git-send-email-bbhatt@xxxxxxxxxxxxxx

Removed "Link" and applied to mhi-next!

Thanks,
Mani

> ---
>  drivers/bus/mhi/core/main.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index 22acde1..fc9196f 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -773,11 +773,18 @@ static void mhi_process_cmd_completion(struct mhi_controller *mhi_cntrl,
>  	cmd_pkt = mhi_to_virtual(mhi_ring, ptr);
>  
>  	chan = MHI_TRE_GET_CMD_CHID(cmd_pkt);
> -	mhi_chan = &mhi_cntrl->mhi_chan[chan];
> -	write_lock_bh(&mhi_chan->lock);
> -	mhi_chan->ccs = MHI_TRE_GET_EV_CODE(tre);
> -	complete(&mhi_chan->completion);
> -	write_unlock_bh(&mhi_chan->lock);
> +
> +	if (chan < mhi_cntrl->max_chan &&
> +	    mhi_cntrl->mhi_chan[chan].configured) {
> +		mhi_chan = &mhi_cntrl->mhi_chan[chan];
> +		write_lock_bh(&mhi_chan->lock);
> +		mhi_chan->ccs = MHI_TRE_GET_EV_CODE(tre);
> +		complete(&mhi_chan->completion);
> +		write_unlock_bh(&mhi_chan->lock);
> +	} else {
> +		dev_err(&mhi_cntrl->mhi_dev->dev,
> +			"Completion packet for invalid channel ID: %d\n", chan);
> +	}
>  
>  	mhi_del_ring_element(mhi_cntrl, mhi_ring);
>  }
> -- 
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