Re: [PATCH net-next] net: ipv4: clear dev->ip_ptr before destroying inetdev

[Ido Schimmel]

On Tue, Jul 07, 2026 at 01:30:39PM +0900, Yuyang Huang wrote:
> To prevent RCU readers from accessing a partially destroyed in_device,
> clear dev->ip_ptr early in inetdev_destroy() before freeing the
> multicast list and individual IP addresses. This aligns the IPv4 teardown
> sequence with the IPv6 implementation.
> 
> Cc: Ido Schimmel <idosch@xxxxxxxxxx>
> Cc: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
> Signed-off-by: Yuyang Huang <yuyanghuang@xxxxxxxxxx>

I believe that sashiko-gemini [1] is right and you need to teach
prestera to ignore NETDEV_DOWN notifications in the inetaddr chain when
a RIF doesn't exist. Something like [2].

Regarding ieee80211_ifa_changed(), the net device is being tore down, so
failing to update the firmware ARP filter probably doesn't matter, but
you can do something like [3] to avoid it completely.

So, three patches where the last one aligns IPv4 with IPv6. Please check
if other listeners need to be adjusted (mlxsw is OK).

Thanks

[1] https://sashiko.dev/#/patchset/20260707043039.101983-1-yuyanghuang%40google.com

[2]
diff --git a/drivers/net/ethernet/marvell/prestera/prestera_router.c b/drivers/net/ethernet/marvell/prestera/prestera_router.c
index b036b173a308..0c4f462baa6e 100644
--- a/drivers/net/ethernet/marvell/prestera/prestera_router.c
+++ b/drivers/net/ethernet/marvell/prestera/prestera_router.c
@@ -1302,10 +1302,8 @@ static int __prestera_inetaddr_port_event(struct net_device *port_dev,
 		dev_hold(port_dev);
 		break;
 	case NETDEV_DOWN:
-		if (!re) {
-			NL_SET_ERR_MSG_MOD(extack, "Can't find RIF");
-			return -EEXIST;
-		}
+		if (!re)
+			return 0;
 		prestera_rif_entry_destroy(port->sw, re);
 		dev_put(port_dev);
 		break;

[3]
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 90d295cc364f..0e7a60dd1d8d 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -588,9 +588,7 @@ static int ieee80211_ifa_changed(struct notifier_block *nb,
 	if (sdata->vif.type != NL80211_IFTYPE_STATION)
 		return NOTIFY_DONE;
 
-	idev = __in_dev_get_rtnl(sdata->dev);
-	if (!idev)
-		return NOTIFY_DONE;
+	idev = ifa->ifa_dev;
 
 	ifmgd = &sdata->u.mgd;