net: phylink: avoid resolving link state too early

During testing on Armada 388 platforms, it was found with a certain
module configuration that it was possible to trigger a kernel oops
during the module load process, caused by the phylink resolver being
triggered for a currently disabled interface.

This problem was introduced by changing the way the SFP registration
works, which now can result in the sfp link down notification being
called during phylink_create().

Fixes: b5bfc21a ("net: sfp: do not probe SFP module before we're attached")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/phylink.c

@@ -474,6 +474,17 @@ static void phylink_run_resolve(struct phylink *pl)
 		queue_work(system_power_efficient_wq, &pl->resolve);
 }
 
+static void phylink_run_resolve_and_disable(struct phylink *pl, int bit)
+{
+	unsigned long state = pl->phylink_disable_state;
+
+	set_bit(bit, &pl->phylink_disable_state);
+	if (state == 0) {
+		queue_work(system_power_efficient_wq, &pl->resolve);
+		flush_work(&pl->resolve);
+	}
+}
+
 static void phylink_fixed_poll(struct timer_list *t)
 {
 	struct phylink *pl = container_of(t, struct phylink, link_poll);
@@ -924,9 +935,7 @@ void phylink_stop(struct phylink *pl)
 	if (pl->link_an_mode == MLO_AN_FIXED && !IS_ERR(pl->link_gpio))
 		del_timer_sync(&pl->link_poll);
 
-	set_bit(PHYLINK_DISABLE_STOPPED, &pl->phylink_disable_state);
-	queue_work(system_power_efficient_wq, &pl->resolve);
-	flush_work(&pl->resolve);
+	phylink_run_resolve_and_disable(pl, PHYLINK_DISABLE_STOPPED);
 }
 EXPORT_SYMBOL_GPL(phylink_stop);
 
@@ -1632,9 +1641,7 @@ static void phylink_sfp_link_down(void *upstream)
 
 	ASSERT_RTNL();
 
-	set_bit(PHYLINK_DISABLE_LINK, &pl->phylink_disable_state);
-	queue_work(system_power_efficient_wq, &pl->resolve);
-	flush_work(&pl->resolve);
+	phylink_run_resolve_and_disable(pl, PHYLINK_DISABLE_LINK);
 }
 
 static void phylink_sfp_link_up(void *upstream)