[PATCH net-next v4 2/6] net: stmmac: close the interface after a failed MTU reopen

[James Hilliard <james.hilliard1@gmail.com>]

An MTU change stops the data path and then reopens it using a newly
allocated DMA configuration. If reopening fails, the new allocation is
freed while the netdev remains up and priv->dma_conf retains copies of
the freed pointers. A subsequent close repeats NAPI disable and IRQ and
DMA-resource teardown. It can hang in napi_disable() or access resources
which have already been freed.

Track successful opens of the data path separately from the netdev's
administrative state. Clear that state when releasing the data path and
skip a second release after a failed reopen. Close the netdev through the
network core on the MTU error path, so the PHY attachment and runtime-PM
reference are released and the interface is marked down. A subsequent
open can then allocate fresh resources and retry normally.

Keep successful MTU changes on the existing path, retaining the PHY
attachment and runtime-PM reference. Allocation failures before stopping
the original data path still leave the running interface unchanged.

Fixes: 3470079687448 ("net: ethernet: stmicro: stmmac: permit MTU change with interface up")
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac.h      |  2 ++
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 10 ++++++++++
 2 files changed, 12 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index 4fc96b317d79..363872ff00d6 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -281,6 +281,8 @@ struct stmmac_priv {
 	struct mutex lock;
 
 	struct stmmac_dma_conf dma_conf;
+	/* Paired __stmmac_open()/__stmmac_release(), serialized by RTNL. */
+	bool opened;
 
 	/* Generic channel for NAPI */
 	struct stmmac_channel channel[STMMAC_CH_MAX];
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index bf9e7e4cb1c3..89b773370894 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4212,6 +4212,7 @@ static int __stmmac_open(struct net_device *dev,
 	stmmac_enable_all_queues(priv);
 	netif_tx_start_all_queues(priv->dev);
 	stmmac_enable_all_dma_irq(priv);
+	priv->opened = true;
 
 	return 0;
 
@@ -4287,6 +4288,11 @@ static void __stmmac_release(struct net_device *dev)
 	struct stmmac_priv *priv = netdev_priv(dev);
 	u8 chan;
 
+	/* A failed MTU reopen has already released the data path. */
+	if (!priv->opened)
+		return;
+	priv->opened = false;
+
 	/* Stop and disconnect the PHY */
 	phylink_stop(priv->phylink);
 
@@ -6212,6 +6218,10 @@ static int stmmac_change_mtu(struct net_device *dev, int new_mtu)
 		if (ret) {
 			free_dma_desc_resources(priv, dma_conf);
 			kfree(dma_conf);
+			/* Finish closing the PHY and PM state, but do not repeat
+			 * the data-path teardown after the failed reopen.
+			 */
+			netif_close(dev);
 			netdev_err(priv->dev, "failed reopening the interface after MTU change\n");
 			return ret;
 		}

-- 
2.53.0