linux-kernel - [PATCH 5.7 001/477] staging: wfx: fix potential deadlock in wfx_tx

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Date:   Tue, 23 Jun 2020 21:49:58 +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, Dan Carpenter <dan.carpenter@...cle.com>,
        Jérôme Pouiller 
        <jerome.pouiller@...abs.com>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.7 001/477] staging: wfx: fix potential deadlock in wfx_tx_flush()

From: Jérôme Pouiller <jerome.pouiller@...abs.com>

[ Upstream commit a39e761aa4fefa2a8aaf549217329933b91da7c9 ]

wfx_tx_flush() wait there are no more frame in device buffer. However,
this event may never happens since wfx_tx_flush() don't forbid to
enqueue new frames.

Note that wfx_tx_flush() should only ensure that all frames currently in
hardware queues are sent. So the current code is more restrictive that
it should.

Note that wfx_tx_flush() release the lock before to return while
wfx_tx_lock_flush() keep the lock.

Reviewed-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Jérôme Pouiller <jerome.pouiller@...abs.com>
Link: https://lore.kernel.org/r/20200401110405.80282-31-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/staging/wfx/queue.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/staging/wfx/queue.c b/drivers/staging/wfx/queue.c
index 39d9127ce4b9f..8ae23681e29bc 100644
--- a/drivers/staging/wfx/queue.c
+++ b/drivers/staging/wfx/queue.c
@@ -35,6 +35,7 @@ void wfx_tx_flush(struct wfx_dev *wdev)
 	if (wdev->chip_frozen)
 		return;
 
+	wfx_tx_lock(wdev);
 	mutex_lock(&wdev->hif_cmd.lock);
 	ret = wait_event_timeout(wdev->hif.tx_buffers_empty,
 				 !wdev->hif.tx_buffers_used,
@@ -47,6 +48,7 @@ void wfx_tx_flush(struct wfx_dev *wdev)
 		wdev->chip_frozen = 1;
 	}
 	mutex_unlock(&wdev->hif_cmd.lock);
+	wfx_tx_unlock(wdev);
 }
 
 void wfx_tx_lock_flush(struct wfx_dev *wdev)
-- 
2.25.1