Patch "net: Fix data-races around sysctl_devconf_inherit_init_net." has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: Fix data-races around sysctl_devconf_inherit_init_net.

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-fix-data-races-around-sysctl_devconf_inherit_ini.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 8869d29426a4533dbecf1fbc670aae5601c2ab58
Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Date:   Tue Aug 23 10:46:57 2022 -0700

    net: Fix data-races around sysctl_devconf_inherit_init_net.
    
    [ Upstream commit a5612ca10d1aa05624ebe72633e0c8c792970833 ]
    
    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@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index f9ed41ca7ac6d..3b97438afe3e2 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -636,6 +636,15 @@ 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 4744c7839de53..9ac41ffdc6344 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -2673,23 +2673,27 @@ 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 6dcf034835ecd..8800987fdb402 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -7128,9 +7128,8 @@ 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));