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arp: Get dev after calling arp_req_(delete|set|get)(). 

arp_ioctl() holds rtnl_lock() first regardless of cmd (SIOCDARP,
SIOCSARP, and SIOCGARP) to get net_device by __dev_get_by_name()
and copy dev->name safely.

In the SIOCGARP path, arp_req_get() calls neigh_lookup(), which
looks up a neighbour entry under RCU.

We will extend the RCU section not to take rtnl_lock() and instead
use dev_get_by_name_rcu() for SIOCGARP.

As a preparation, let's move __dev_get_by_name() into another
function and call it from arp_req_delete(), arp_req_set(), and
arp_req_get().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240430015813.71143-6-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima 2024-04-29 18:58:11 -07:00 committed by Jakub Kicinski
parent 51e9ba48d4
commit a428bfc77a
1 changed files with 50 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

86
net/ipv4/arp.c
View File

@ -1003,12 +1003,36 @@ out_of_mem:
* User level interface (ioctl)
*/
static struct net_device *arp_req_dev_by_name(struct net *net, struct arpreq *r)
{
struct net_device *dev;
dev = __dev_get_by_name(net, r->arp_dev);
if (!dev)
return ERR_PTR(-ENODEV);
/* Mmmm... It is wrong... ARPHRD_NETROM == 0 */
if (!r->arp_ha.sa_family)
r->arp_ha.sa_family = dev->type;
if ((r->arp_flags & ATF_COM) && r->arp_ha.sa_family != dev->type)
return ERR_PTR(-EINVAL);
return dev;
}
static struct net_device *arp_req_dev(struct net *net, struct arpreq *r)
{
struct net_device *dev;
struct rtable *rt;
__be32 ip;
if (r->arp_dev[0])
return arp_req_dev_by_name(net, r);
if (r->arp_flags & ATF_PUBL)
return NULL;
ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
rt = ip_route_output(net, ip, 0, 0, 0, RT_SCOPE_LINK);
@ -1063,21 +1087,20 @@ static int arp_req_set_public(struct net *net, struct arpreq *r,
return arp_req_set_proxy(net, dev, 1);
}
static int arp_req_set(struct net *net, struct arpreq *r,
struct net_device *dev)
static int arp_req_set(struct net *net, struct arpreq *r)
{
struct neighbour *neigh;
struct net_device *dev;
__be32 ip;
int err;
dev = arp_req_dev(net, r);
if (IS_ERR(dev))
return PTR_ERR(dev);
if (r->arp_flags & ATF_PUBL)
return arp_req_set_public(net, r, dev);
if (!dev) {
dev = arp_req_dev(net, r);
if (IS_ERR(dev))
return PTR_ERR(dev);
}
switch (dev->type) {
#if IS_ENABLED(CONFIG_FDDI)
case ARPHRD_FDDI:
@ -1134,10 +1157,18 @@ static unsigned int arp_state_to_flags(struct neighbour *neigh)
* Get an ARP cache entry.
*/
static int arp_req_get(struct arpreq *r, struct net_device *dev)
static int arp_req_get(struct net *net, struct arpreq *r)
{
__be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
struct neighbour *neigh;
struct net_device *dev;
if (!r->arp_dev[0])
return -ENODEV;
dev = arp_req_dev_by_name(net, r);
if (IS_ERR(dev))
return PTR_ERR(dev);
neigh = neigh_lookup(&arp_tbl, &ip, dev);
if (!neigh)
@ -1201,20 +1232,20 @@ static int arp_req_delete_public(struct net *net, struct arpreq *r,
return arp_req_set_proxy(net, dev, 0);
}
static int arp_req_delete(struct net *net, struct arpreq *r,
struct net_device *dev)
static int arp_req_delete(struct net *net, struct arpreq *r)
{
struct net_device *dev;
__be32 ip;
dev = arp_req_dev(net, r);
if (IS_ERR(dev))
return PTR_ERR(dev);
if (r->arp_flags & ATF_PUBL)
return arp_req_delete_public(net, r, dev);
ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
if (!dev) {
dev = arp_req_dev(net, r);
if (IS_ERR(dev))
return PTR_ERR(dev);
}
return arp_invalidate(dev, ip, true);
}
@ -1224,7 +1255,6 @@ static int arp_req_delete(struct net *net, struct arpreq *r,
int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
{
struct net_device *dev = NULL;
struct arpreq r;
__be32 *netmask;
int err;
@ -1258,35 +1288,19 @@ int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
return -EINVAL;
rtnl_lock();
if (r.arp_dev[0]) {
err = -ENODEV;
dev = __dev_get_by_name(net, r.arp_dev);
if (!dev)
goto out;
/* Mmmm... It is wrong... ARPHRD_NETROM==0 */
if (!r.arp_ha.sa_family)
r.arp_ha.sa_family = dev->type;
err = -EINVAL;
if ((r.arp_flags & ATF_COM) && r.arp_ha.sa_family != dev->type)
goto out;
} else if (cmd == SIOCGARP) {
err = -ENODEV;
goto out;
}
switch (cmd) {
case SIOCDARP:
err = arp_req_delete(net, &r, dev);
err = arp_req_delete(net, &r);
break;
case SIOCSARP:
err = arp_req_set(net, &r, dev);
err = arp_req_set(net, &r);
break;
case SIOCGARP:
err = arp_req_get(&r, dev);
err = arp_req_get(net, &r);
break;
}
out:
rtnl_unlock();
if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
err = -EFAULT;