net: check all name nodes in __dev_alloc_name

[ Upstream commit 6c015a2256801597fadcbc11d287774c9c512fa5 ]

__dev_alloc_name(), when supplied with a name containing '%d',
will search for the first available device number to generate a
unique device name.

Since commit ff92741270bf8b6e78aa885f166b68c7a67ab13a ("net:
introduce name_node struct to be used in hashlist") network
devices may have alternate names.  __dev_alloc_name() does take
these alternate names into account, possibly generating a name
that is already taken and failing with -ENFILE as a result.

This demonstrates the bug:

    # rmmod dummy 2>/dev/null
    # ip link property add dev lo altname dummy0
    # modprobe dummy numdummies=1
    modprobe: ERROR: could not insert 'dummy': Too many open files in system

Instead of creating a device named dummy1, modprobe fails.

Fix this by checking all the names in the d->name_node list, not just d->name.

Signed-off-by: Jiri Bohac <jbohac@suse.cz>
Fixes: ff92741270bf ("net: introduce name_node struct to be used in hashlist")
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/core/dev.c b/net/core/dev.c
index 75ca6c6d01d6eda7461c639bdd91b0c0caed830d..dbc286fd2047b87b013125d6de595efb2f5a1045 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1195,6 +1195,18 @@ static int __dev_alloc_name(struct net *net, const char *name, char *buf)
                        return -ENOMEM;
 
                for_each_netdev(net, d) {
+                       struct netdev_name_node *name_node;
+                       list_for_each_entry(name_node, &d->name_node->list, list) {
+                               if (!sscanf(name_node->name, name, &i))
+                                       continue;
+                               if (i < 0 || i >= max_netdevices)
+                                       continue;
+
+                               /*  avoid cases where sscanf is not exact inverse of printf */
+                               snprintf(buf, IFNAMSIZ, name, i);
+                               if (!strncmp(buf, name_node->name, IFNAMSIZ))
+                                       set_bit(i, inuse);
+                       }
                        if (!sscanf(d->name, name, &i))
                                continue;
                        if (i < 0 || i >= max_netdevices)