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rtnetlink: do not acquire RTNL in rtnl_getlink() with RTEXT_FILTER_NAME_ONLY

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When RTEXT_FILTER_NAME_ONLY is requested, rtnl_fill_ifinfo()
is dumping device attributes which do not need RTNL protection.

Many shell scripts invoke iproute2 commands specifying a device by
its name. After this patch, they will no longer add RTNL pressure.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260525083542.1565964-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet
2026-05-25 08:35:40 +00:00
committed by Jakub Kicinski
parent 00888feb60
commit e896e5c073
1 changed files with 68 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files

96
net/core/rtnetlink.c
View File

@@ -2068,7 +2068,6 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
struct nlmsghdr *nlh;
struct Qdisc *qdisc;
ASSERT_RTNL();
nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ifm), flags);
if (nlh == NULL)
return -EMSGSIZE;
@@ -2091,6 +2090,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
if (ext_filter_mask & RTEXT_FILTER_NAME_ONLY)
goto end;
ASSERT_RTNL();
if (tgt_netnsid >= 0 &&
nla_put_s32(skb, IFLA_TARGET_NETNSID, tgt_netnsid))
goto nla_put_failure;
@@ -3468,6 +3468,21 @@ static struct net_device *rtnl_dev_get(struct net *net,
return __dev_get_by_name(net, ifname);
}
static struct net_device *rtnl_dev_get_rcu(struct net *net,
struct nlattr *tb[])
{
char ifname[ALTIFNAMSIZ];
if (tb[IFLA_IFNAME])
nla_strscpy(ifname, tb[IFLA_IFNAME], IFNAMSIZ);
else if (tb[IFLA_ALT_IFNAME])
nla_strscpy(ifname, tb[IFLA_ALT_IFNAME], ALTIFNAMSIZ);
else
return NULL;
return dev_get_by_name_rcu(net, ifname);
}
static int rtnl_setlink(struct sk_buff *skb, struct nlmsghdr *nlh,
struct netlink_ext_ack *extack)
{
@@ -4187,14 +4202,16 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr *nlh,
struct netlink_ext_ack *extack)
{
struct net *net = sock_net(skb->sk);
struct net *tgt_net = net;
struct ifinfomsg *ifm;
struct nlattr *tb[IFLA_MAX+1];
struct nlattr *tb[IFLA_MAX + 1];
netdevice_tracker dev_tracker;
struct net_device *dev = NULL;
struct net *tgt_net = net;
u32 ext_filter_mask = 0;
struct ifinfomsg *ifm;
struct sk_buff *nskb;
int netnsid = -1;
bool need_rtnl;
int err;
u32 ext_filter_mask = 0;
err = rtnl_valid_getlink_req(skb, nlh, tb, extack);
if (err < 0)
@@ -4214,43 +4231,65 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr *nlh,
if (tb[IFLA_EXT_MASK])
ext_filter_mask = nla_get_u32(tb[IFLA_EXT_MASK]);
err = -EINVAL;
ifm = nlmsg_data(nlh);
if (ifm->ifi_index > 0)
dev = __dev_get_by_index(tgt_net, ifm->ifi_index);
else if (tb[IFLA_IFNAME] || tb[IFLA_ALT_IFNAME])
dev = rtnl_dev_get(tgt_net, tb);
else
rcu_read_lock();
if (ifm->ifi_index > 0) {
dev = dev_get_by_index_rcu(tgt_net, ifm->ifi_index);
} else if (tb[IFLA_IFNAME] || tb[IFLA_ALT_IFNAME]) {
dev = rtnl_dev_get_rcu(tgt_net, tb);
} else {
rcu_read_unlock();
err = -EINVAL;
goto out;
}
netdev_hold(dev, &dev_tracker, GFP_ATOMIC);
rcu_read_unlock();
err = -ENODEV;
if (dev == NULL)
goto out;
need_rtnl = !(ext_filter_mask & RTEXT_FILTER_NAME_ONLY);
retry:
if (need_rtnl) {
rtnl_lock();
/* Synchronize the carrier state so we don't report a state
* that we're not actually going to honour immediately; if
* the driver just did a carrier off->on transition, we can
* only TX if link watch work has run, but without this we'd
* already report carrier on, even if it doesn't work yet.
*/
linkwatch_sync_dev(dev);
}
err = -ENOBUFS;
nskb = nlmsg_new_large(if_nlmsg_size(dev, ext_filter_mask));
if (nskb == NULL)
goto out;
if (nskb)
err = rtnl_fill_ifinfo(nskb, dev, net,
RTM_NEWLINK, NETLINK_CB(skb).portid,
nlh->nlmsg_seq, 0, 0, ext_filter_mask,
0, NULL, 0, netnsid, GFP_KERNEL);
/* Synchronize the carrier state so we don't report a state
* that we're not actually going to honour immediately; if
* the driver just did a carrier off->on transition, we can
* only TX if link watch work has run, but without this we'd
* already report carrier on, even if it doesn't work yet.
*/
linkwatch_sync_dev(dev);
if (need_rtnl)
rtnl_unlock();
err = rtnl_fill_ifinfo(nskb, dev, net,
RTM_NEWLINK, NETLINK_CB(skb).portid,
nlh->nlmsg_seq, 0, 0, ext_filter_mask,
0, NULL, 0, netnsid, GFP_KERNEL);
if (err < 0) {
/* -EMSGSIZE implies BUG in if_nlmsg_size */
WARN_ON(err == -EMSGSIZE);
kfree_skb(nskb);
} else
if (err == -EMSGSIZE) {
if (!need_rtnl) {
/* Some altnames were added, retry with RTNL. */
need_rtnl = true;
goto retry;
}
/* -EMSGSIZE implies BUG in if_nlmsg_size */
WARN_ON_ONCE(1);
}
} else {
err = rtnl_unicast(nskb, net, NETLINK_CB(skb).portid);
}
out:
netdev_put(dev, &dev_tracker);
if (netnsid >= 0)
put_net(tgt_net);
@@ -7117,7 +7156,8 @@ static const struct rtnl_msg_handler rtnetlink_rtnl_msg_handlers[] __initconst =
{.msgtype = RTM_DELLINK, .doit = rtnl_dellink,
.flags = RTNL_FLAG_DOIT_PERNET_WIP},
{.msgtype = RTM_GETLINK, .doit = rtnl_getlink,
.dumpit = rtnl_dump_ifinfo, .flags = RTNL_FLAG_DUMP_SPLIT_NLM_DONE},
.dumpit = rtnl_dump_ifinfo,
.flags = RTNL_FLAG_DUMP_SPLIT_NLM_DONE | RTNL_FLAG_DOIT_UNLOCKED},
{.msgtype = RTM_SETLINK, .doit = rtnl_setlink,
.flags = RTNL_FLAG_DOIT_PERNET_WIP},
{.msgtype = RTM_GETADDR, .dumpit = rtnl_dump_all},