net: faraday: ftmac100: remove netif_running(netdev) check before disabling interrupts

BugLink: https://bugs.launchpad.net/bugs/1811077

[ Upstream commit 426a593e ]

In the original ftmac100_interrupt(), the interrupts are only disabled when
the condition "netif_running(netdev)" is true. However, this condition
causes kerenl hang in the following case. When the user requests to
disable the network device, kernel will clear the bit __LINK_STATE_START
from the dev->state and then call the driver's ndo_stop function. Network
device interrupts are not blocked during this process. If an interrupt
occurs between clearing __LINK_STATE_START and stopping network device,
kernel cannot disable the interrupts due to the condition
"netif_running(netdev)" in the ISR. Hence, kernel will hang due to the
continuous interruption of the network device.

In order to solve the above problem, the interrupts of the network device
should always be disabled in the ISR without being restricted by the
condition "netif_running(netdev)".

[V2]
Remove unnecessary curly braces.
Signed-off-by: Vincent Chen <vincentc@andestech.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/net/ethernet/faraday/ftmac100.c

@@ -865,11 +865,10 @@ static irqreturn_t ftmac100_interrupt(int irq, void *dev_id)
 	struct net_device *netdev = dev_id;
 	struct ftmac100 *priv = netdev_priv(netdev);
 
-	if (likely(netif_running(netdev))) {
 	/* Disable interrupts for polling */
 	ftmac100_disable_all_int(priv);
+	if (likely(netif_running(netdev)))
 		napi_schedule(&priv->napi);
-	}
 
 	return IRQ_HANDLED;
 }