Re: [syzbot] [net?] BUG: sleeping function called from invalid context in synchronize_net

[Hillf Danton <hdanton@sina.com>]

On Thu, 11 Jul 2024 14:10:22 -0700
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    523b23f0bee3 Add linux-next specific files for 20240710
> git tree:       linux-next
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10ec9585980000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git  523b23f0bee3

--- x/net/ethtool/ioctl.c
+++ y/net/ethtool/ioctl.c
@@ -58,10 +58,11 @@ static struct devlink *netdev_to_devlink
 
 u32 ethtool_op_get_link(struct net_device *dev)
 {
-	/* Synchronize carrier state with link watch, see also rtnl_getlink() */
-	linkwatch_sync_dev(dev);
+	u32 rc = netif_carrier_ok(dev) ? 1 : 0;
 
-	return netif_carrier_ok(dev) ? 1 : 0;
+	linkwatch_fire_event(NULL);
+
+	return rc;
 }
 EXPORT_SYMBOL(ethtool_op_get_link);
 
--- x/net/core/link_watch.c
+++ y/net/core/link_watch.c
@@ -286,13 +286,17 @@ static void linkwatch_event(struct work_
 
 void linkwatch_fire_event(struct net_device *dev)
 {
-	bool urgent = linkwatch_urgent_event(dev);
+	bool urgent = true;
 
+	if (!dev)
+		goto sched;
+	urgent = linkwatch_urgent_event(dev);
 	if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
 		linkwatch_add_event(dev);
 	} else if (!urgent)
 		return;
 
+sched:
 	linkwatch_schedule_work(urgent);
 }
 EXPORT_SYMBOL(linkwatch_fire_event);
--