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net: check all name nodes in __dev_alloc_name

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[ 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 ff92741270 ("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: ff92741270 ("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>
This commit is contained in:
Jiri Bohac 2021-03-18 04:42:53 +01:00 committed by Greg Kroah-Hartman
parent 748a158359
commit 943e1583bf
1 changed files with 12 additions and 0 deletions
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12
net/core/dev.c
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@ -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)