From: Haiyang Zhang <haiyangz@linux•microsoft.com>
To: linux-hyperv@vger•kernel.org, netdev@vger•kernel.org
Cc: haiyangz@microsoft•com, kys@microsoft•com, wei.liu@kernel•org,
edumazet@google•com, kuba@kernel•org, pabeni@redhat•com,
horms@kernel•org, davem@davemloft•net, sdf@fomichev•me,
kuniyu@google•com, ahmed.zaki@intel•com,
aleksander.lobakin@intel•com, linux-kernel@vger•kernel.org,
stable@vger•kernel.org, #@linux.microsoft.com,
5.4+@linux•microsoft.com
Subject: [PATCH net] net: core: Fix the loop in default_device_exit_net()
Date: Fri, 18 Jul 2025 13:20:14 -0700 [thread overview]
Message-ID: <1752870014-28909-1-git-send-email-haiyangz@linux.microsoft.com> (raw)
From: Haiyang Zhang <haiyangz@microsoft•com>
The loop in default_device_exit_net() won't be able to properly detect the
head then stop, and will hit NULL pointer, when a driver, like hv_netvsc,
automatically moves the slave device together with the master device.
To fix this, add a helper function to return the first migratable netdev
correctly, no matter one or two devices were removed from this net's list
in the last iteration.
Cc: stable@vger•kernel.org # 5.4+
Signed-off-by: Haiyang Zhang <haiyangz@microsoft•com>
---
net/core/dev.c | 31 +++++++++++++++++++++----------
1 file changed, 21 insertions(+), 10 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 621a639aeba1..d83f5f12cf70 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -12629,19 +12629,11 @@ static struct pernet_operations __net_initdata netdev_net_ops = {
.exit = netdev_exit,
};
-static void __net_exit default_device_exit_net(struct net *net)
+static inline struct net_device *first_migratable_netdev(struct net *net)
{
- struct netdev_name_node *name_node, *tmp;
struct net_device *dev, *aux;
- /*
- * Push all migratable network devices back to the
- * initial network namespace
- */
- ASSERT_RTNL();
- for_each_netdev_safe(net, dev, aux) {
- int err;
- char fb_name[IFNAMSIZ];
+ for_each_netdev_safe(net, dev, aux) {
/* Ignore unmoveable devices (i.e. loopback) */
if (dev->netns_immutable)
continue;
@@ -12650,6 +12642,25 @@ static void __net_exit default_device_exit_net(struct net *net)
if (dev->rtnl_link_ops && !dev->rtnl_link_ops->netns_refund)
continue;
+ return dev;
+ }
+
+ return NULL;
+}
+
+static void __net_exit default_device_exit_net(struct net *net)
+{
+ struct netdev_name_node *name_node, *tmp;
+ struct net_device *dev;
+ /*
+ * Push all migratable network devices back to the
+ * initial network namespace
+ */
+ ASSERT_RTNL();
+ while ((dev = first_migratable_netdev(net)) != NULL) {
+ int err;
+ char fb_name[IFNAMSIZ];
+
/* Push remaining network devices to init_net */
snprintf(fb_name, IFNAMSIZ, "dev%d", dev->ifindex);
if (netdev_name_in_use(&init_net, fb_name))
--
2.34.1
next reply other threads:[~2025-07-18 20:21 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-18 20:20 Haiyang Zhang [this message]
2025-07-18 23:37 ` [PATCH net] net: core: Fix the loop in default_device_exit_net() Jakub Kicinski
2025-07-19 20:47 ` Kuniyuki Iwashima
2025-07-22 16:20 ` [EXTERNAL] " Haiyang Zhang
2025-07-22 6:51 ` Eric Dumazet
2025-07-22 16:15 ` [EXTERNAL] " Haiyang Zhang
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