linux-kernel - [PATCH 4.19 122/271] wil6210: drop old event after wmi

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Message-Id: <20190724191705.729673847@linuxfoundation.org>
Date:   Wed, 24 Jul 2019 21:19:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ahmad Masri <amasri@...eaurora.org>,
        Maya Erez <merez@...eaurora.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 122/271] wil6210: drop old event after wmi_call timeout

[ Upstream commit 1a276003111c0404f6bfeffe924c5a21f482428b ]

This change fixes a rare race condition of handling WMI events after
wmi_call expires.

wmi_recv_cmd immediately handles an event when reply_buf is defined and
a wmi_call is waiting for the event.
However, in case the wmi_call has already timed-out, there will be no
waiting/running wmi_call and the event will be queued in WMI queue and
will be handled later in wmi_event_handle.
Meanwhile, a new similar wmi_call for the same command and event may
be issued. In this case, when handling the queued event we got WARN_ON
printed.

Fixing this case as a valid timeout and drop the unexpected event.

Signed-off-by: Ahmad Masri <amasri@...eaurora.org>
Signed-off-by: Maya Erez <merez@...eaurora.org>
Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/wireless/ath/wil6210/wmi.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/wil6210/wmi.c b/drivers/net/wireless/ath/wil6210/wmi.c
index 6e3b3031f29b..2010f771478d 100644
--- a/drivers/net/wireless/ath/wil6210/wmi.c
+++ b/drivers/net/wireless/ath/wil6210/wmi.c
@@ -2816,7 +2816,18 @@ static void wmi_event_handle(struct wil6210_priv *wil,
 		/* check if someone waits for this event */
 		if (wil->reply_id && wil->reply_id == id &&
 		    wil->reply_mid == mid) {
-			WARN_ON(wil->reply_buf);
+			if (wil->reply_buf) {
+				/* event received while wmi_call is waiting
+				 * with a buffer. Such event should be handled
+				 * in wmi_recv_cmd function. Handling the event
+				 * here means a previous wmi_call was timeout.
+				 * Drop the event and do not handle it.
+				 */
+				wil_err(wil,
+					"Old event (%d, %s) while wmi_call is waiting. Drop it and Continue waiting\n",
+					id, eventid2name(id));
+				return;
+			}
 
 			wmi_evt_call_handler(vif, id, evt_data,
 					     len - sizeof(*wmi));
-- 
2.20.1