netdev - [PATCH net] net: fec: Better handle pm_runtime

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Date: Wed, 10 May 2023 22:00:20 +0200
From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To: Wei Fang <wei.fang@....com>,
	Shenwei Wang <shenwei.wang@....com>,
	Clark Wang <xiaoning.wang@....com>,
	NXP Linux Team <linux-imx@....com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Fugang Duan <fugang.duan@....com>,
	Chuhong Yuan <hslester96@...il.com>,
	netdev@...r.kernel.org,
	kernel@...gutronix.de
Subject: [PATCH net] net: fec: Better handle pm_runtime_get() failing in .remove()

In the (unlikely) event that pm_runtime_get() (disguised as
pm_runtime_resume_and_get()) fails, the remove callback returned an
error early. The problem with this is that the driver core ignores the
error value and continues removing the device. This results in a
resource leak. Worse the devm allocated resources are freed and so if a
callback of the driver is called later the register mapping is already
gone which probably results in a crash.

Fixes: a31eda65ba21 ("net: fec: fix clock count mis-match")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
---
 drivers/net/ethernet/freescale/fec_main.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 42ec6ca3bf03..241df41d500f 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -4478,9 +4478,11 @@ fec_drv_remove(struct platform_device *pdev)
 	struct device_node *np = pdev->dev.of_node;
 	int ret;
 
-	ret = pm_runtime_resume_and_get(&pdev->dev);
+	ret = pm_runtime_get_sync(&pdev->dev);
 	if (ret < 0)
-		return ret;
+		dev_err(&pdev->dev,
+			"Failed to resume device in remove callback (%pe)\n",
+			ERR_PTR(ret));
 
 	cancel_work_sync(&fep->tx_timeout_work);
 	fec_ptp_stop(pdev);
@@ -4493,8 +4495,13 @@ fec_drv_remove(struct platform_device *pdev)
 		of_phy_deregister_fixed_link(np);
 	of_node_put(fep->phy_node);
 
-	clk_disable_unprepare(fep->clk_ahb);
-	clk_disable_unprepare(fep->clk_ipg);
+	/* After pm_runtime_get_sync() failed, the clks are still off, so skip
+	 * disabling them again.
+	 */
+	if (ret >= 0) {
+		clk_disable_unprepare(fep->clk_ahb);
+		clk_disable_unprepare(fep->clk_ipg);
+	}
 	pm_runtime_put_noidle(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 
base-commit: ac9a78681b921877518763ba0e89202254349d1b
-- 
2.39.2