Re: [PATCH v2] bus: mhi: core: Sanity check values from remote device before use

[Manivannan Sadhasivam]

On Wed, Feb 17, 2021 at 09:20:22AM -0700, Jeffrey Hugo wrote:
> When parsing the structures in the shared memory, there are values which
> come from the remote device.  For example, a transfer completion event
> will have a pointer to the tre in the relevant channel's transfer ring.
> Such values should be considered to be untrusted, and validated before
> use.  If we blindly use such values, we may access invalid data or crash
> if the values are corrupted.
> 
> If validation fails, drop the relevant event.
> 
> Signed-off-by: Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>
> ---
> 
> v2: Fix subject
> 
>  drivers/bus/mhi/core/main.c | 81 +++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 74 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index c043574..1eb2fd3 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -242,6 +242,11 @@ static void mhi_del_ring_element(struct mhi_controller *mhi_cntrl,
>  	smp_wmb();
>  }
>  
> +static bool is_valid_ring_ptr(struct mhi_ring *ring, dma_addr_t addr)
> +{
> +	return addr >= ring->iommu_base && addr < ring->iommu_base + ring->len;
> +}
> +
>  int mhi_destroy_device(struct device *dev, void *data)
>  {
>  	struct mhi_device *mhi_dev;
> @@ -383,7 +388,16 @@ irqreturn_t mhi_irq_handler(int irq_number, void *dev)
>  	struct mhi_event_ctxt *er_ctxt =
>  		&mhi_cntrl->mhi_ctxt->er_ctxt[mhi_event->er_index];
>  	struct mhi_ring *ev_ring = &mhi_event->ring;
> -	void *dev_rp = mhi_to_virtual(ev_ring, er_ctxt->rp);
> +	dma_addr_t ptr = er_ctxt->rp;
> +	void *dev_rp;
> +
> +	if (!is_valid_ring_ptr(ev_ring, ptr)) {
> +		dev_err(&mhi_cntrl->mhi_dev->dev,
> +			"Event ring rp points outside of the event ring\n");
> +		return IRQ_HANDLED;
> +	}
> +
> +	dev_rp = mhi_to_virtual(ev_ring, ptr);
>  
>  	/* Only proceed if event ring has pending events */
>  	if (ev_ring->rp == dev_rp)
> @@ -536,6 +550,11 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl,
>  		struct mhi_buf_info *buf_info;
>  		u16 xfer_len;
>  
> +		if (!is_valid_ring_ptr(tre_ring, ptr)) {
> +			dev_err(&mhi_cntrl->mhi_dev->dev,
> +				"Event element points outside of the tre ring\n");
> +			break;
> +		}
>  		/* Get the TRB this event points to */
>  		ev_tre = mhi_to_virtual(tre_ring, ptr);
>  
> @@ -695,6 +714,12 @@ static void mhi_process_cmd_completion(struct mhi_controller *mhi_cntrl,
>  	struct mhi_chan *mhi_chan;
>  	u32 chan;
>  
> +	if (!is_valid_ring_ptr(mhi_ring, ptr)) {
> +		dev_err(&mhi_cntrl->mhi_dev->dev,
> +			"Event element points outside of the cmd ring\n");
> +		return;
> +	}
> +
>  	cmd_pkt = mhi_to_virtual(mhi_ring, ptr);
>  
>  	chan = MHI_TRE_GET_CMD_CHID(cmd_pkt);
> @@ -719,6 +744,7 @@ int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
>  	struct device *dev = &mhi_cntrl->mhi_dev->dev;
>  	u32 chan;
>  	int count = 0;
> +	dma_addr_t ptr = er_ctxt->rp;
>  
>  	/*
>  	 * This is a quick check to avoid unnecessary event processing
> @@ -728,7 +754,13 @@ int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
>  	if (unlikely(MHI_EVENT_ACCESS_INVALID(mhi_cntrl->pm_state)))
>  		return -EIO;
>  
> -	dev_rp = mhi_to_virtual(ev_ring, er_ctxt->rp);
> +	if (!is_valid_ring_ptr(ev_ring, ptr)) {
> +		dev_err(&mhi_cntrl->mhi_dev->dev,
> +			"Event ring rp points outside of the event ring\n");
> +		return -EIO;
> +	}
> +
> +	dev_rp = mhi_to_virtual(ev_ring, ptr);
>  	local_rp = ev_ring->rp;
>  
>  	while (dev_rp != local_rp) {
> @@ -834,6 +866,8 @@ int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
>  			 */
>  			if (chan < mhi_cntrl->max_chan) {
>  				mhi_chan = &mhi_cntrl->mhi_chan[chan];
> +				if (!mhi_chan->configured)
> +					break;

This change is not part of this patch I believe.

>  				parse_xfer_event(mhi_cntrl, local_rp, mhi_chan);
>  				event_quota--;
>  			}
> @@ -845,7 +879,15 @@ int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
>  
>  		mhi_recycle_ev_ring_element(mhi_cntrl, ev_ring);
>  		local_rp = ev_ring->rp;
> -		dev_rp = mhi_to_virtual(ev_ring, er_ctxt->rp);
> +
> +		ptr = er_ctxt->rp;
> +		if (!is_valid_ring_ptr(ev_ring, ptr)) {
> +			dev_err(&mhi_cntrl->mhi_dev->dev,
> +				"Event ring rp points outside of the event ring\n");
> +			return -EIO;
> +		}
> +
> +		dev_rp = mhi_to_virtual(ev_ring, ptr);
>  		count++;
>  	}
>  
> @@ -868,11 +910,18 @@ int mhi_process_data_event_ring(struct mhi_controller *mhi_cntrl,
>  	int count = 0;
>  	u32 chan;
>  	struct mhi_chan *mhi_chan;
> +	dma_addr_t ptr = er_ctxt->rp;
>  
>  	if (unlikely(MHI_EVENT_ACCESS_INVALID(mhi_cntrl->pm_state)))
>  		return -EIO;
>  
> -	dev_rp = mhi_to_virtual(ev_ring, er_ctxt->rp);
> +	if (!is_valid_ring_ptr(ev_ring, ptr)) {
> +		dev_err(&mhi_cntrl->mhi_dev->dev,
> +			"Event ring rp points outside of the event ring\n");
> +		return -EIO;
> +	}
> +
> +	dev_rp = mhi_to_virtual(ev_ring, ptr);
>  	local_rp = ev_ring->rp;
>  
>  	while (dev_rp != local_rp && event_quota > 0) {
> @@ -886,7 +935,8 @@ int mhi_process_data_event_ring(struct mhi_controller *mhi_cntrl,
>  		 * Only process the event ring elements whose channel
>  		 * ID is within the maximum supported range.
>  		 */
> -		if (chan < mhi_cntrl->max_chan) {
> +		if (chan < mhi_cntrl->max_chan &&
> +		    mhi_cntrl->mhi_chan[chan].configured) {

Same here.

Thanks,
Mani

>  			mhi_chan = &mhi_cntrl->mhi_chan[chan];
>  
>  			if (likely(type == MHI_PKT_TYPE_TX_EVENT)) {
> @@ -900,7 +950,15 @@ int mhi_process_data_event_ring(struct mhi_controller *mhi_cntrl,
>  
>  		mhi_recycle_ev_ring_element(mhi_cntrl, ev_ring);
>  		local_rp = ev_ring->rp;
> -		dev_rp = mhi_to_virtual(ev_ring, er_ctxt->rp);
> +
> +		ptr = er_ctxt->rp;
> +		if (!is_valid_ring_ptr(ev_ring, ptr)) {
> +			dev_err(&mhi_cntrl->mhi_dev->dev,
> +				"Event ring rp points outside of the event ring\n");
> +			return -EIO;
> +		}
> +
> +		dev_rp = mhi_to_virtual(ev_ring, ptr);
>  		count++;
>  	}
>  	read_lock_bh(&mhi_cntrl->pm_lock);
> @@ -1365,6 +1423,7 @@ static void mhi_mark_stale_events(struct mhi_controller *mhi_cntrl,
>  	struct mhi_ring *ev_ring;
>  	struct device *dev = &mhi_cntrl->mhi_dev->dev;
>  	unsigned long flags;
> +	dma_addr_t ptr;
>  
>  	dev_dbg(dev, "Marking all events for chan: %d as stale\n", chan);
>  
> @@ -1372,7 +1431,15 @@ static void mhi_mark_stale_events(struct mhi_controller *mhi_cntrl,
>  
>  	/* mark all stale events related to channel as STALE event */
>  	spin_lock_irqsave(&mhi_event->lock, flags);
> -	dev_rp = mhi_to_virtual(ev_ring, er_ctxt->rp);
> +
> +	ptr = er_ctxt->rp;
> +	if (!is_valid_ring_ptr(ev_ring, ptr)) {
> +		dev_err(&mhi_cntrl->mhi_dev->dev,
> +			"Event ring rp points outside of the event ring\n");
> +		dev_rp = ev_ring->rp;
> +	} else {
> +		dev_rp = mhi_to_virtual(ev_ring, ptr);
> +	}
>  
>  	local_rp = ev_ring->rp;
>  	while (dev_rp != local_rp) {
> -- 
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