[PATCH] net: mvneta: bm: fix device reference leak on failed lookup

[Johan Hovold <johan@kernel.org>]

Make sure to drop the reference taken to the buffer manager device when
attempting to look up its driver data before the driver has been bound.

Note that holding a reference to a device does not prevent its driver
data from going away.

Fixes: 965cbbec7f20 ("net: mvneta: remove data pointer usage from device_node structure")
Cc: stable@vger.kernel.org	# 4.19
Cc: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/net/ethernet/marvell/mvneta_bm.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvneta_bm.c b/drivers/net/ethernet/marvell/mvneta_bm.c
index 6bb380494919..128fe1f512b4 100644
--- a/drivers/net/ethernet/marvell/mvneta_bm.c
+++ b/drivers/net/ethernet/marvell/mvneta_bm.c
@@ -395,9 +395,20 @@ static void mvneta_bm_put_sram(struct mvneta_bm *priv)
 
 struct mvneta_bm *mvneta_bm_get(struct device_node *node)
 {
-	struct platform_device *pdev = of_find_device_by_node(node);
+	struct platform_device *pdev;
+	struct mvneta_bm *priv;
+
+	pdev = of_find_device_by_node(node);
+	if (!pdev)
+		return NULL;
+
+	priv = platform_get_drvdata(pdev);
+	if (!priv) {
+		platform_device_put(pdev);
+		return NULL;
+	}
 
-	return pdev ? platform_get_drvdata(pdev) : NULL;
+	return priv;
 }
 EXPORT_SYMBOL_GPL(mvneta_bm_get);
 
-- 
2.54.0