[PATCH v2 net 14/17] net: Fix data-races around sysctl_devconf_inherit_init_net.

[Kuniyuki Iwashima <kuniyu@amazon.com>]

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

Fixes: 856c395cfa63 ("net: introduce a knob to control whether to inherit devconf config")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
CC: Cong Wang <xiyou.wangcong@gmail.com>
---
 net/ipv4/devinet.c  | 6 ++++--
 net/ipv6/addrconf.c | 2 +-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 92b778e423df..e92428f44f9b 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -2682,8 +2682,10 @@ static __net_init int devinet_init_net(struct net *net)
 #endif
 
 	if (!net_eq(net, &init_net)) {
+		int devconf_inherit_init_net = READ_ONCE(sysctl_devconf_inherit_init_net);
+
 		if (IS_ENABLED(CONFIG_SYSCTL) &&
-		    sysctl_devconf_inherit_init_net == 3) {
+		    devconf_inherit_init_net == 3) {
 			/* copy from the current netns */
 			memcpy(all, current->nsproxy->net_ns->ipv4.devconf_all,
 			       sizeof(ipv4_devconf));
@@ -2691,7 +2693,7 @@ static __net_init int devinet_init_net(struct net *net)
 			       current->nsproxy->net_ns->ipv4.devconf_dflt,
 			       sizeof(ipv4_devconf_dflt));
 		} else if (!IS_ENABLED(CONFIG_SYSCTL) ||
-			   sysctl_devconf_inherit_init_net != 2) {
+			   devconf_inherit_init_net != 2) {
 			/* inherit == 0 or 1: copy from init_net */
 			memcpy(all, init_net.ipv4.devconf_all,
 			       sizeof(ipv4_devconf));
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index b624e3d8c5f0..ac55b02bbe22 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -7164,7 +7164,7 @@ static int __net_init addrconf_init_net(struct net *net)
 
 	if (IS_ENABLED(CONFIG_SYSCTL) &&
 	    !net_eq(net, &init_net)) {
-		switch (sysctl_devconf_inherit_init_net) {
+		switch (READ_ONCE(sysctl_devconf_inherit_init_net)) {
 		case 1:  /* copy from init_net */
 			memcpy(all, init_net.ipv6.devconf_all,
 			       sizeof(ipv6_devconf));
-- 
2.30.2