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net: check for altname conflicts when changing netdev's netns

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It's currently possible to create an altname conflicting
with an altname or real name of another device by creating
it in another netns and moving it over:

 [ ~]$ ip link add dev eth0 type dummy

 [ ~]$ ip netns add test
 [ ~]$ ip -netns test link add dev ethX netns test type dummy
 [ ~]$ ip -netns test link property add dev ethX altname eth0
 [ ~]$ ip -netns test link set dev ethX netns 1

 [ ~]$ ip link
 ...
 3: eth0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
     link/ether 02:40:88:62:ec:b8 brd ff:ff:ff:ff:ff:ff
 ...
 5: ethX: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
     link/ether 26:b7:28:78:38:0f brd ff:ff:ff:ff:ff:ff
     altname eth0

Create a macro for walking the altnames, this hopefully makes
it clearer that the list we walk contains only altnames.
Which is otherwise not entirely intuitive.

Fixes: 36fbf1e52b ("net: rtnetlink: add linkprop commands to add and delete alternative ifnames")
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Jakub Kicinski 2023-10-17 18:38:14 -07:00 committed by Paolo Abeni
parent 311cca4066
commit 7663d52209
2 changed files with 11 additions and 1 deletions
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9
net/core/dev.c
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@ -1086,7 +1086,8 @@ static int __dev_alloc_name(struct net *net, const char *name, char *buf)
for_each_netdev(net, d) {
struct netdev_name_node *name_node;
list_for_each_entry(name_node, &d->name_node->list, list) {
netdev_for_each_altname(d, name_node) {
if (!sscanf(name_node->name, name, &i))
continue;
if (i < 0 || i >= max_netdevices)
@ -11051,6 +11052,7 @@ EXPORT_SYMBOL(unregister_netdev);
int __dev_change_net_namespace(struct net_device *dev, struct net *net,
const char *pat, int new_ifindex)
{
struct netdev_name_node *name_node;
struct net *net_old = dev_net(dev);
char new_name[IFNAMSIZ] = {};
int err, new_nsid;
@ -11083,6 +11085,11 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
if (err < 0)
goto out;
}
/* Check that none of the altnames conflicts. */
err = -EEXIST;
netdev_for_each_altname(dev, name_node)
if (netdev_name_in_use(net, name_node->name))
goto out;
/* Check that new_ifindex isn't used yet. */
if (new_ifindex) {

3
net/core/dev.h
View File

@ -62,6 +62,9 @@ struct netdev_name_node {
int netdev_get_name(struct net *net, char *name, int ifindex);
int dev_change_name(struct net_device *dev, const char *newname);
#define netdev_for_each_altname(dev, namenode) \
list_for_each_entry((namenode), &(dev)->name_node->list, list)
int netdev_name_node_alt_create(struct net_device *dev, const char *name);
int netdev_name_node_alt_destroy(struct net_device *dev, const char *name);