[SRU][F][PATCH 2/2] net: fec: remove .ndo_poll_controller to avoid deadlocks

[Massimiliano Pellizzer]

From: Wei Fang <wei.fang at nxp.com>

There is a deadlock issue found in sungem driver, please refer to the
commit ac0a230f719b ("eth: sungem: remove .ndo_poll_controller to avoid
deadlocks"). The root cause of the issue is that netpoll is in atomic
context and disable_irq() is called by .ndo_poll_controller interface
of sungem driver, however, disable_irq() might sleep. After analyzing
the implementation of fec_poll_controller(), the fec driver should have
the same issue. Due to the fec driver uses NAPI for TX completions, the
.ndo_poll_controller is unnecessary to be implemented in the fec driver,
so fec_poll_controller() can be safely removed.

Fixes: 7f5c6addcdc0 ("net/fec: add poll controller function for fec nic")
Signed-off-by: Wei Fang <wei.fang at nxp.com>
Link: https://lore.kernel.org/r/20240511062009.652918-1-wei.fang@nxp.com
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
(backported from commit c2e0c58b25a0a0c37ec643255558c5af4450c9f5)
[mpellizzer: backported solving merge conflicts due to surrounding
instructions which do not affect the patch]
CVE-2024-38597
Signed-off-by: Massimiliano Pellizzer <massimiliano.pellizzer at canonical.com>
---
 drivers/net/ethernet/freescale/fec_main.c | 26 -----------------------
 1 file changed, 26 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index f11824a078e9..8782ca4e1d5a 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -3179,29 +3179,6 @@ fec_set_mac_address(struct net_device *ndev, void *p)
 	return 0;
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-/**
- * fec_poll_controller - FEC Poll controller function
- * @dev: The FEC network adapter
- *
- * Polled functionality used by netconsole and others in non interrupt mode
- *
- */
-static void fec_poll_controller(struct net_device *dev)
-{
-	int i;
-	struct fec_enet_private *fep = netdev_priv(dev);
-
-	for (i = 0; i < FEC_IRQ_NUM; i++) {
-		if (fep->irq[i] > 0) {
-			disable_irq(fep->irq[i]);
-			fec_enet_interrupt(fep->irq[i], dev);
-			enable_irq(fep->irq[i]);
-		}
-	}
-}
-#endif
-
 static inline void fec_enet_set_netdev_features(struct net_device *netdev,
 	netdev_features_t features)
 {
@@ -3250,9 +3227,6 @@ static const struct net_device_ops fec_netdev_ops = {
 	.ndo_tx_timeout		= fec_timeout,
 	.ndo_set_mac_address	= fec_set_mac_address,
 	.ndo_do_ioctl		= fec_enet_ioctl,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller	= fec_poll_controller,
-#endif
 	.ndo_set_features	= fec_set_features,
 };
 
-- 
2.43.0