[PATCH 5.10 096/108] ipv6: annotate data-races around cnf.disable_ipv6

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@xxxxxxxxxx>

commit d289ab65b89c1d4d88417cb6c03e923f21f95fae upstream.

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>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
[Ashwin: Regenerated the Patch for v5.10]
Signed-off-by: Ashwin Dayanand Kamat <ashwin.kamat@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ipv6/addrconf.c   |    9 +++++----
 net/ipv6/ip6_input.c  |    2 +-
 net/ipv6/ip6_output.c |    2 +-
 3 files changed, 7 insertions(+), 6 deletions(-)

--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4107,7 +4107,7 @@ static void addrconf_dad_work(struct wor
 			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);
@@ -6220,7 +6220,8 @@ static void addrconf_disable_change(stru
 		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);
 		}
@@ -6237,7 +6238,7 @@ static int addrconf_disable_ipv6(struct
 
 	net = (struct net *)table->extra2;
 	old = *p;
-	*p = newf;
+	WRITE_ONCE(*p, newf);
 
 	if (p == &net->ipv6.devconf_dflt->disable_ipv6) {
 		rtnl_unlock();
@@ -6245,7 +6246,7 @@ static int addrconf_disable_ipv6(struct
 	}
 
 	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);
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -165,7 +165,7 @@ static struct sk_buff *ip6_rcv_core(stru
 	__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;
 	}
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -240,7 +240,7 @@ int ip6_output(struct net *net, struct s
 	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;