net: Fix data-races around sysctl_devconf_inherit_init_net.

While reading sysctl_devconf_inherit_init_net, it can be changed
concurrently.  Thus, we need to add READ_ONCE() to its readers.

Fixes: 6f31b347aa9c ("net: introduce a knob to control whether to inherit devconf config")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 6d3a33fd0cdb3d287c40faf0382708595851bd16..05d6f3facd5a5e6935f2ae94114a40f5365df669 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -650,6 +650,15 @@ static inline bool net_has_fallback_tunnels(const struct net *net)
 #endif
 }
 
+static inline int net_inherit_devconf(void)
+{
+#if IS_ENABLED(CONFIG_SYSCTL)
+       return READ_ONCE(sysctl_devconf_inherit_init_net);
+#else
+       return 0;
+#endif
+}
+
 static inline int netdev_queue_numa_node_read(const struct netdev_queue *q)
 {
 #if defined(CONFIG_XPS) && defined(CONFIG_NUMA)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 92b778e423df824d45ffbfa53a975af14c6c5713..e8b9a9202fecd913137f169f161dfdccc16f7edf 100644 (file)
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -2682,23 +2682,27 @@ static __net_init int devinet_init_net(struct net *net)
 #endif
 
        if (!net_eq(net, &init_net)) {
-               if (IS_ENABLED(CONFIG_SYSCTL) &&
-                   sysctl_devconf_inherit_init_net == 3) {
+               switch (net_inherit_devconf()) {
+               case 3:
                        /* copy from the current netns */
                        memcpy(all, current->nsproxy->net_ns->ipv4.devconf_all,
                               sizeof(ipv4_devconf));
                        memcpy(dflt,
                               current->nsproxy->net_ns->ipv4.devconf_dflt,
                               sizeof(ipv4_devconf_dflt));
-               } else if (!IS_ENABLED(CONFIG_SYSCTL) ||
-                          sysctl_devconf_inherit_init_net != 2) {
-                       /* inherit == 0 or 1: copy from init_net */
+                       break;
+               case 0:
+               case 1:
+                       /* copy from init_net */
                        memcpy(all, init_net.ipv4.devconf_all,
                               sizeof(ipv4_devconf));
                        memcpy(dflt, init_net.ipv4.devconf_dflt,
                               sizeof(ipv4_devconf_dflt));
+                       break;
+               case 2:
+                       /* use compiled values */
+                       break;
                }
-               /* else inherit == 2: use compiled values */
        }
 
 #ifdef CONFIG_SYSCTL

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index b624e3d8c5f0a5062879d8cbfacfc37d138afc3a..e15f64f22fa8327a4e4211c299ecee9cbcf41d26 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -7162,9 +7162,8 @@ static int __net_init addrconf_init_net(struct net *net)
        if (!dflt)
                goto err_alloc_dflt;
 
-       if (IS_ENABLED(CONFIG_SYSCTL) &&
-           !net_eq(net, &init_net)) {
-               switch (sysctl_devconf_inherit_init_net) {
+       if (!net_eq(net, &init_net)) {
+               switch (net_inherit_devconf()) {
                case 1:  /* copy from init_net */
                        memcpy(all, init_net.ipv6.devconf_all,
                               sizeof(ipv6_devconf));