[PATCH v7 3/8] bus: mhi: core: Add range check for channel id received in event ring

[Bhaumik Bhatt <bbhatt@codeaurora.org>]

From: Hemant Kumar <hemantk@codeaurora.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@codeaurora.org>
Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Jeffrey Hugo <jhugo@codeaurora.org>
---
 drivers/bus/mhi/core/main.c | 40 +++++++++++++++++++++++++++++-----------
 1 file changed, 29 insertions(+), 11 deletions(-)

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index 605640c..30798ec 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -775,9 +775,18 @@ int mhi_process_ctrl_ev_ring(struct mhi_controller *mhi_cntrl,
 		}
 		case MHI_PKT_TYPE_TX_EVENT:
 			chan = MHI_TRE_GET_EV_CHID(local_rp);
-			mhi_chan = &mhi_cntrl->mhi_chan[chan];
-			parse_xfer_event(mhi_cntrl, local_rp, mhi_chan);
-			event_quota--;
+
+			WARN_ON(chan >= mhi_cntrl->max_chan);
+
+			/*
+			 * Only process the event ring elements whose channel
+			 * ID is within the maximum supported range.
+			 */
+			if (chan < mhi_cntrl->max_chan) {
+				mhi_chan = &mhi_cntrl->mhi_chan[chan];
+				parse_xfer_event(mhi_cntrl, local_rp, mhi_chan);
+				event_quota--;
+			}
 			break;
 		default:
 			dev_err(dev, "Unhandled event type: %d\n", type);
@@ -820,14 +829,23 @@ 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);
-		mhi_chan = &mhi_cntrl->mhi_chan[chan];
-
-		if (likely(type == MHI_PKT_TYPE_TX_EVENT)) {
-			parse_xfer_event(mhi_cntrl, local_rp, mhi_chan);
-			event_quota--;
-		} else if (type == MHI_PKT_TYPE_RSC_TX_EVENT) {
-			parse_rsc_event(mhi_cntrl, local_rp, mhi_chan);
-			event_quota--;
+
+		WARN_ON(chan >= mhi_cntrl->max_chan);
+
+		/*
+		 * Only process the event ring elements whose channel
+		 * ID is within the maximum supported range.
+		 */
+		if (chan < mhi_cntrl->max_chan) {
+			mhi_chan = &mhi_cntrl->mhi_chan[chan];
+
+			if (likely(type == MHI_PKT_TYPE_TX_EVENT)) {
+				parse_xfer_event(mhi_cntrl, local_rp, mhi_chan);
+				event_quota--;
+			} else if (type == MHI_PKT_TYPE_RSC_TX_EVENT) {
+				parse_rsc_event(mhi_cntrl, local_rp, mhi_chan);
+				event_quota--;
+			}
 		}
 
 		mhi_recycle_ev_ring_element(mhi_cntrl, ev_ring);
-- 
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