[PATCH 5.15 054/201] ip: Fix data-races around sysctl_ip_no_pmtu_disc.

[Greg Kroah-Hartman]

From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>

[ Upstream commit 0968d2a441bf6afb551fd99e60fa65ed67068963 ]

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

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/ipv4/af_inet.c    | 2 +-
 net/ipv4/icmp.c       | 2 +-
 net/ipv6/af_inet6.c   | 2 +-
 net/xfrm/xfrm_state.c | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 44f21278003d..781c595f6880 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -338,7 +338,7 @@ static int inet_create(struct net *net, struct socket *sock, int protocol,
 			inet->hdrincl = 1;
 	}
 
-	if (net->ipv4.sysctl_ip_no_pmtu_disc)
+	if (READ_ONCE(net->ipv4.sysctl_ip_no_pmtu_disc))
 		inet->pmtudisc = IP_PMTUDISC_DONT;
 	else
 		inet->pmtudisc = IP_PMTUDISC_WANT;
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index a5cc89506c1e..609c4ff7edc6 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -887,7 +887,7 @@ static bool icmp_unreach(struct sk_buff *skb)
 			 * values please see
 			 * Documentation/networking/ip-sysctl.rst
 			 */
-			switch (net->ipv4.sysctl_ip_no_pmtu_disc) {
+			switch (READ_ONCE(net->ipv4.sysctl_ip_no_pmtu_disc)) {
 			default:
 				net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n",
 						    &iph->daddr);
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index dab4a047590b..3a91d0d40aec 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -226,7 +226,7 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol,
 	RCU_INIT_POINTER(inet->mc_list, NULL);
 	inet->rcv_tos	= 0;
 
-	if (net->ipv4.sysctl_ip_no_pmtu_disc)
+	if (READ_ONCE(net->ipv4.sysctl_ip_no_pmtu_disc))
 		inet->pmtudisc = IP_PMTUDISC_DONT;
 	else
 		inet->pmtudisc = IP_PMTUDISC_WANT;
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index f7bfa1916968..b1a04a22166f 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -2619,7 +2619,7 @@ int __xfrm_init_state(struct xfrm_state *x, bool init_replay, bool offload)
 	int err;
 
 	if (family == AF_INET &&
-	    xs_net(x)->ipv4.sysctl_ip_no_pmtu_disc)
+	    READ_ONCE(xs_net(x)->ipv4.sysctl_ip_no_pmtu_disc))
 		x->props.flags |= XFRM_STATE_NOPMTUDISC;
 
 	err = -EPROTONOSUPPORT;
-- 
2.35.1