linux-kernel - [PATCH 4/4] firmware: arm_scmi: Fix handling of unexpected delayed responses

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Message-Id: <20200420152315.21008-5-cristian.marussi@arm.com>
Date:   Mon, 20 Apr 2020 16:23:15 +0100
From:   Cristian Marussi <cristian.marussi@....com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     sudeep.holla@....com, cristian.marussi@....com
Subject: [PATCH 4/4] firmware: arm_scmi: Fix handling of unexpected delayed responses

Upon reception of an unexpected bogus delayed response, clear the channel
and bail-out safely.

Fixes: 4d09852b6f01 ("firmware: arm_scmi: Add support for notifications message processing")
Signed-off-by: Cristian Marussi <cristian.marussi@....com>
---
 drivers/firmware/arm_scmi/driver.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 07de196f15aa..0146332d06a1 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -247,6 +247,21 @@ static void scmi_handle_response(struct scmi_chan_info *cinfo,
 	}
 
 	xfer = &minfo->xfer_block[xfer_id];
+	/*
+	 * Even if a response was indeed expected on this slot at this point,
+	 * a buggy platform could wrongly reply feeding us an unexpected
+	 * delayed response we're not prepared to handle: bail-out safely
+	 * blaming fw guys.
+	 */
+	if (unlikely(msg_type == MSG_TYPE_DELAYED_RESP && !xfer->async_done)) {
+		dev_err(dev,
+			"Delayed Response for %d not expected! Buggy FW ?\n",
+			xfer_id);
+		info->desc->ops->clear_channel(cinfo);
+		/* It was unexpected, so nobody will clear the xfer if not us */
+		__scmi_xfer_put(minfo, xfer);
+		return;
+	}
 
 	scmi_dump_header_dbg(dev, &xfer->hdr);
 
-- 
2.17.1