neighbour: Convert RTM_GETNEIGH to RCU.

Only __dev_get_by_index() is the RTNL dependant in neigh_get().

Let's replace it with dev_get_by_index_rcu() and convert RTM_GETNEIGH
to RCU.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-10-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 59dfdecddff3f0cde84d7b7d8851525d013196a7..50ab95ecbcd6a07b2441058a70cc9a6b4cbe68d7 100644 (file)
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -3049,27 +3049,29 @@ static int neigh_get(struct sk_buff *in_skb, struct nlmsghdr *nlh,
        if (!skb)
                return -ENOBUFS;
 
+       rcu_read_lock();
+
        tbl = neigh_find_table(ndm->ndm_family);
        if (!tbl) {
                NL_SET_ERR_MSG(extack, "Unsupported family in header for neighbor get request");
                err = -EAFNOSUPPORT;
-               goto err_free_skb;
+               goto err_unlock;
        }
 
        if (nla_len(tb[NDA_DST]) != (int)tbl->key_len) {
                NL_SET_ERR_MSG(extack, "Invalid network address in neighbor get request");
                err = -EINVAL;
-               goto err_free_skb;
+               goto err_unlock;
        }
 
        dst = nla_data(tb[NDA_DST]);
 
        if (ndm->ndm_ifindex) {
-               dev = __dev_get_by_index(net, ndm->ndm_ifindex);
+               dev = dev_get_by_index_rcu(net, ndm->ndm_ifindex);
                if (!dev) {
                        NL_SET_ERR_MSG(extack, "Unknown device ifindex");
                        err = -ENODEV;
-                       goto err_free_skb;
+                       goto err_unlock;
                }
        }
 
@@ -3080,28 +3082,31 @@ static int neigh_get(struct sk_buff *in_skb, struct nlmsghdr *nlh,
                if (!pn) {
                        NL_SET_ERR_MSG(extack, "Proxy neighbour entry not found");
                        err = -ENOENT;
-                       goto err_free_skb;
+                       goto err_unlock;
                }
 
                err = pneigh_fill_info(skb, pn, pid, seq, RTM_NEWNEIGH, 0, tbl);
                if (err)
-                       goto err_free_skb;
+                       goto err_unlock;
        } else {
                neigh = neigh_lookup(tbl, dst, dev);
                if (!neigh) {
                        NL_SET_ERR_MSG(extack, "Neighbour entry not found");
                        err = -ENOENT;
-                       goto err_free_skb;
+                       goto err_unlock;
                }
 
                err = neigh_fill_info(skb, neigh, pid, seq, RTM_NEWNEIGH, 0);
                neigh_release(neigh);
                if (err)
-                       goto err_free_skb;
+                       goto err_unlock;
        }
 
+       rcu_read_unlock();
+
        return rtnl_unicast(skb, net, pid);
-err_free_skb:
+err_unlock:
+       rcu_read_unlock();
        kfree_skb(skb);
        return err;
 }
@@ -3904,7 +3909,7 @@ static const struct rtnl_msg_handler neigh_rtnl_msg_handlers[] __initconst = {
        {.msgtype = RTM_NEWNEIGH, .doit = neigh_add},
        {.msgtype = RTM_DELNEIGH, .doit = neigh_delete},
        {.msgtype = RTM_GETNEIGH, .doit = neigh_get, .dumpit = neigh_dump_info,
-        .flags = RTNL_FLAG_DUMP_UNLOCKED},
+        .flags = RTNL_FLAG_DOIT_UNLOCKED | RTNL_FLAG_DUMP_UNLOCKED},
        {.msgtype = RTM_GETNEIGHTBL, .dumpit = neightbl_dump_info},
        {.msgtype = RTM_SETNEIGHTBL, .doit = neightbl_set},
 };