netdev - [PATCH v3 net-next 2/2] net: ethernet: mtk_wed: fix possible deadlock if mtk_wed_wo

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Message-Id: <b28b55a639002a56b77c0651a4122ebede041936.1670421354.git.lorenzo@kernel.org>
Date:   Wed,  7 Dec 2022 15:04:55 +0100
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     netdev@...r.kernel.org
Cc:     nbd@....name, john@...ozen.org, sean.wang@...iatek.com,
        Mark-MC.Lee@...iatek.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, matthias.bgg@...il.com,
        linux-mediatek@...ts.infradead.org, lorenzo.bianconi@...hat.com,
        leon@...nel.org, sujuan.chen@...iatek.com
Subject: [PATCH v3 net-next 2/2] net: ethernet: mtk_wed: fix possible deadlock if mtk_wed_wo_init fails

Introduce __mtk_wed_detach() in order to avoid a deadlock in
mtk_wed_attach routine if mtk_wed_wo_init fails since both
mtk_wed_attach and mtk_wed_detach run holding hw_lock mutex.

Fixes: 4c5de09eb0d0 ("net: ethernet: mtk_wed: add configure wed wo support")
Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
---
 drivers/net/ethernet/mediatek/mtk_wed.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/mediatek/mtk_wed.c b/drivers/net/ethernet/mediatek/mtk_wed.c
index 4ef23eadd69e..a6271449617f 100644
--- a/drivers/net/ethernet/mediatek/mtk_wed.c
+++ b/drivers/net/ethernet/mediatek/mtk_wed.c
@@ -577,12 +577,10 @@ mtk_wed_deinit(struct mtk_wed_device *dev)
 }
 
 static void
-mtk_wed_detach(struct mtk_wed_device *dev)
+__mtk_wed_detach(struct mtk_wed_device *dev)
 {
 	struct mtk_wed_hw *hw = dev->hw;
 
-	mutex_lock(&hw_lock);
-
 	mtk_wed_deinit(dev);
 
 	mtk_wdma_rx_reset(dev);
@@ -615,6 +613,13 @@ mtk_wed_detach(struct mtk_wed_device *dev)
 	module_put(THIS_MODULE);
 
 	hw->wed_dev = NULL;
+}
+
+static void
+mtk_wed_detach(struct mtk_wed_device *dev)
+{
+	mutex_lock(&hw_lock);
+	__mtk_wed_detach(dev);
 	mutex_unlock(&hw_lock);
 }
 
@@ -1497,8 +1502,10 @@ mtk_wed_attach(struct mtk_wed_device *dev)
 		ret = mtk_wed_wo_init(hw);
 	}
 out:
-	if (ret)
-		mtk_wed_detach(dev);
+	if (ret) {
+		dev_err(dev->hw->dev, "failed to attach wed device\n");
+		__mtk_wed_detach(dev);
+	}
 unlock:
 	mutex_unlock(&hw_lock);
 
-- 
2.38.1