[PATCH v5.15 1/2] net/ipv6: annotate data-races around cnf.disable_ipv6

[Ashwin Kamat]

From: Eric Dumazet <edumazet@xxxxxxxxxx>

[Upstream commit d289ab65b89c1d4d88417cb6c03e923f21f95fae]

disable_ipv6 is read locklessly, add appropriate READ_ONCE()
and WRITE_ONCE() annotations.

v2: do not preload net before rtnl_trylock() in
    addrconf_disable_ipv6() (Jiri)

Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Stable-dep-of: 4db783d68b9b ("ipv6: prevent NULL dereference in ip6_output()")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
[Ashwin: Regenerated the Patch for v5.15]
Signed-off-by: Ashwin Dayanand Kamat <ashwin.kamat@xxxxxxxxxxxx>
---
 net/ipv6/addrconf.c   | 9 +++++----
 net/ipv6/ip6_input.c  | 2 +-
 net/ipv6/ip6_output.c | 2 +-
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index a17e1d744b2d..ba22470b7476 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4131,7 +4131,7 @@ static void addrconf_dad_work(struct work_struct *w)
 			if (!ipv6_generate_eui64(addr.s6_addr + 8, idev->dev) &&
 			    ipv6_addr_equal(&ifp->addr, &addr)) {
 				/* DAD failed for link-local based on MAC */
-				idev->cnf.disable_ipv6 = 1;
+				WRITE_ONCE(idev->cnf.disable_ipv6, 1);
 
 				pr_info("%s: IPv6 being disabled!\n",
 					ifp->idev->dev->name);
@@ -6277,7 +6277,8 @@ static void addrconf_disable_change(struct net *net, __s32 newf)
 		idev = __in6_dev_get(dev);
 		if (idev) {
 			int changed = (!idev->cnf.disable_ipv6) ^ (!newf);
-			idev->cnf.disable_ipv6 = newf;
+
+			WRITE_ONCE(idev->cnf.disable_ipv6, newf);
 			if (changed)
 				dev_disable_change(idev);
 		}
@@ -6294,7 +6295,7 @@ static int addrconf_disable_ipv6(struct ctl_table *table, int *p, int newf)
 
 	net = (struct net *)table->extra2;
 	old = *p;
-	*p = newf;
+	WRITE_ONCE(*p, newf);
 
 	if (p == &net->ipv6.devconf_dflt->disable_ipv6) {
 		rtnl_unlock();
@@ -6302,7 +6303,7 @@ static int addrconf_disable_ipv6(struct ctl_table *table, int *p, int newf)
 	}
 
 	if (p == &net->ipv6.devconf_all->disable_ipv6) {
-		net->ipv6.devconf_dflt->disable_ipv6 = newf;
+		WRITE_ONCE(net->ipv6.devconf_dflt->disable_ipv6, newf);
 		addrconf_disable_change(net, newf);
 	} else if ((!newf) ^ (!old))
 		dev_disable_change((struct inet6_dev *)table->extra1);
diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index 32071529bfd9..c1c29432367c 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -164,7 +164,7 @@ static struct sk_buff *ip6_rcv_core(struct sk_buff *skb, struct net_device *dev,
 	__IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_IN, skb->len);
 
 	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
-	    !idev || unlikely(idev->cnf.disable_ipv6)) {
+	    !idev || unlikely(READ_ONCE(idev->cnf.disable_ipv6))) {
 		__IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 		goto drop;
 	}
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 7205473ba28d..770ee7ffb0d5 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -221,7 +221,7 @@ int ip6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 	skb->protocol = htons(ETH_P_IPV6);
 	skb->dev = dev;
 
-	if (unlikely(idev->cnf.disable_ipv6)) {
+	if (unlikely(READ_ONCE(idev->cnf.disable_ipv6))) {
 		IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS);
 		kfree_skb(skb);
 		return 0;
-- 
2.45.1