bus: mhi: core: Validate channel ID when processing command completions

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.

Link: https://lore.kernel.org/r/1624558141-11045-1-git-send-email-bbhatt@codeaurora.org
Fixes: 1d3173a3 ("bus: mhi: core: Add support for processing events from client device")
Cc: stable@vger.kernel.org #5.10
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20210716075106.49938-3-manivannan.sadhasivam@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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);
 }