mpls: Convert RTM_GETNETCONF to RCU.

mpls_netconf_get_devconf() calls __dev_get_by_index(),
and this only depends on RTNL.

Let's convert mpls_netconf_get_devconf() to RCU and use
dev_get_by_index_rcu().

Note that nlmsg_new() is moved ahead to use GFP_KERNEL.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Link: https://patch.msgid.link/20251029173344.2934622-12-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index f00f75c137dc4703967175740657b2d591f2f572..49fd15232dbec75004cbf22809d9b5fa0a31ae85 100644 (file)
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -1282,23 +1282,32 @@ static int mpls_netconf_get_devconf(struct sk_buff *in_skb,
        if (err < 0)
                goto errout;
 
-       err = -EINVAL;
-       if (!tb[NETCONFA_IFINDEX])
+       if (!tb[NETCONFA_IFINDEX]) {
+               err = -EINVAL;
                goto errout;
+       }
 
        ifindex = nla_get_s32(tb[NETCONFA_IFINDEX]);
-       dev = __dev_get_by_index(net, ifindex);
-       if (!dev)
-               goto errout;
-
-       mdev = mpls_dev_get(net, dev);
-       if (!mdev)
-               goto errout;
 
-       err = -ENOBUFS;
        skb = nlmsg_new(mpls_netconf_msgsize_devconf(NETCONFA_ALL), GFP_KERNEL);
-       if (!skb)
+       if (!skb) {
+               err = -ENOBUFS;
                goto errout;
+       }
+
+       rcu_read_lock();
+
+       dev = dev_get_by_index_rcu(net, ifindex);
+       if (!dev) {
+               err = -EINVAL;
+               goto errout_unlock;
+       }
+
+       mdev = mpls_dev_rcu(dev);
+       if (!mdev) {
+               err = -EINVAL;
+               goto errout_unlock;
+       }
 
        err = mpls_netconf_fill_devconf(skb, mdev,
                                        NETLINK_CB(in_skb).portid,
@@ -1307,12 +1316,19 @@ static int mpls_netconf_get_devconf(struct sk_buff *in_skb,
        if (err < 0) {
                /* -EMSGSIZE implies BUG in mpls_netconf_msgsize_devconf() */
                WARN_ON(err == -EMSGSIZE);
-               kfree_skb(skb);
-               goto errout;
+               goto errout_unlock;
        }
+
        err = rtnl_unicast(skb, net, NETLINK_CB(in_skb).portid);
+
+       rcu_read_unlock();
 errout:
        return err;
+
+errout_unlock:
+       rcu_read_unlock();
+       kfree_skb(skb);
+       goto errout;
 }
 
 static int mpls_netconf_dump_devconf(struct sk_buff *skb,
@@ -2776,7 +2792,7 @@ static const struct rtnl_msg_handler mpls_rtnl_msg_handlers[] __initdata_or_modu
         RTNL_FLAG_DUMP_UNLOCKED},
        {THIS_MODULE, PF_MPLS, RTM_GETNETCONF,
         mpls_netconf_get_devconf, mpls_netconf_dump_devconf,
-        RTNL_FLAG_DUMP_UNLOCKED},
+        RTNL_FLAG_DOIT_UNLOCKED | RTNL_FLAG_DUMP_UNLOCKED},
 };
 
 static int __init mpls_init(void)