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arp: Convert ioctl(SIOCGARP) to RCU.

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ioctl(SIOCGARP) holds rtnl_lock() to get netdev by __dev_get_by_name()
and copy dev->name safely and calls neigh_lookup() later, which looks
up a neighbour entry under RCU.

Let's replace __dev_get_by_name() with dev_get_by_name_rcu() and strscpy()
with netdev_copy_name() to avoid locking rtnl_lock().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240430015813.71143-8-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima 2024-04-29 18:58:13 -07:00 committed by Jakub Kicinski
parent 0840556e5a
commit bf4ea58874
1 changed files with 18 additions and 10 deletions
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28
net/ipv4/arp.c
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@ -1003,11 +1003,15 @@ out_of_mem:
* User level interface (ioctl)
*/
static struct net_device *arp_req_dev_by_name(struct net *net, struct arpreq *r)
static struct net_device *arp_req_dev_by_name(struct net *net, struct arpreq *r,
bool getarp)
{
struct net_device *dev;
dev = __dev_get_by_name(net, r->arp_dev);
if (getarp)
dev = dev_get_by_name_rcu(net, r->arp_dev);
else
dev = __dev_get_by_name(net, r->arp_dev);
if (!dev)
return ERR_PTR(-ENODEV);
@ -1028,7 +1032,7 @@ static struct net_device *arp_req_dev(struct net *net, struct arpreq *r)
__be32 ip;
if (r->arp_dev[0])
return arp_req_dev_by_name(net, r);
return arp_req_dev_by_name(net, r, false);
if (r->arp_flags & ATF_PUBL)
return NULL;
@ -1166,7 +1170,7 @@ static int arp_req_get(struct net *net, struct arpreq *r)
if (!r->arp_dev[0])
return -ENODEV;
dev = arp_req_dev_by_name(net, r);
dev = arp_req_dev_by_name(net, r, true);
if (IS_ERR(dev))
return PTR_ERR(dev);
@ -1188,7 +1192,7 @@ static int arp_req_get(struct net *net, struct arpreq *r)
neigh_release(neigh);
r->arp_ha.sa_family = dev->type;
strscpy(r->arp_dev, dev->name, sizeof(r->arp_dev));
netdev_copy_name(dev, r->arp_dev);
return 0;
}
@ -1287,23 +1291,27 @@ int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
else if (*netmask && *netmask != htonl(0xFFFFFFFFUL))
return -EINVAL;
rtnl_lock();
switch (cmd) {
case SIOCDARP:
rtnl_lock();
err = arp_req_delete(net, &r);
rtnl_unlock();
break;
case SIOCSARP:
rtnl_lock();
err = arp_req_set(net, &r);
rtnl_unlock();
break;
case SIOCGARP:
rcu_read_lock();
err = arp_req_get(net, &r);
rcu_read_unlock();
if (!err && copy_to_user(arg, &r, sizeof(r)))
err = -EFAULT;
break;
}
rtnl_unlock();
if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
err = -EFAULT;
return err;
}