ipv6: anycast: Unify two error paths in ipv6_sock_ac_join().

The next patch will replace __dev_get_by_index() and __dev_get_by_flags()
to RCU + refcount version.

Then, we will need to call dev_put() in some error paths.

Let's unify two error paths to make the next patch cleaner.

Note that we add READ_ONCE() for net->ipv6.devconf_all->forwarding
and idev->conf.forwarding as we will drop RTNL that protects them.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250702230210.3115355-14-kuni1840@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv6/anycast.c b/net/ipv6/anycast.c
index 8440e7b27f6d61a551a35d7f5b3bcf949c0abe64..fd3d104c6c05764dc921ed342c8bdace12e2e1d0 100644 (file)
--- a/net/ipv6/anycast.c
+++ b/net/ipv6/anycast.c
@@ -67,12 +67,11 @@ static u32 inet6_acaddr_hash(const struct net *net,
 int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 {
        struct ipv6_pinfo *np = inet6_sk(sk);
+       struct ipv6_ac_socklist *pac = NULL;
+       struct net *net = sock_net(sk);
        struct net_device *dev = NULL;
        struct inet6_dev *idev;
-       struct ipv6_ac_socklist *pac;
-       struct net *net = sock_net(sk);
-       int     ishost = !net->ipv6.devconf_all->forwarding;
-       int     err = 0;
+       int err = 0, ishost;
 
        ASSERT_RTNL();
 
@@ -84,15 +83,22 @@ int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
        if (ifindex)
                dev = __dev_get_by_index(net, ifindex);
 
-       if (ipv6_chk_addr_and_flags(net, addr, dev, true, 0, IFA_F_TENTATIVE))
-               return -EINVAL;
+       if (ipv6_chk_addr_and_flags(net, addr, dev, true, 0, IFA_F_TENTATIVE)) {
+               err = -EINVAL;
+               goto error;
+       }
 
        pac = sock_kmalloc(sk, sizeof(struct ipv6_ac_socklist), GFP_KERNEL);
-       if (!pac)
-               return -ENOMEM;
+       if (!pac) {
+               err = -ENOMEM;
+               goto error;
+       }
+
        pac->acl_next = NULL;
        pac->acl_addr = *addr;
 
+       ishost = !READ_ONCE(net->ipv6.devconf_all->forwarding);
+
        if (ifindex == 0) {
                struct rt6_info *rt;
 
@@ -123,8 +129,9 @@ int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
                        err = -EADDRNOTAVAIL;
                goto error;
        }
+
        /* reset ishost, now that we have a specific device */
-       ishost = !idev->cnf.forwarding;
+       ishost = !READ_ONCE(idev->cnf.forwarding);
 
        pac->acl_ifindex = dev->ifindex;