commit 0968d2a441bf6afb551fd99e60fa65ed67068963
author Kuniyuki Iwashima <kuniyu@amazon.com> Wed Jul 13 13:51:52 2022 -0700
committer David S. Miller <davem@davemloft.net> Fri Jul 15 11:49:55 2022 +0100
tree 94b301f59fbd5390e80493ce1845272c0e644c0e
parent 8281b7ec5c56b71cb2cc5a1728b41607be66959c

ip: Fix data-races around sysctl_ip_no_pmtu_disc.

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@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/af_inet.c

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index ac67f6b..4bc24f9 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -335,7 +335,7 @@ 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;

net/ipv4/icmp.c

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 57c4f0d..d5d745c 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -881,7 +881,7 @@ static enum skb_drop_reason 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);

net/ipv6/af_inet6.c

diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 70564dd..6f354f8 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;

net/xfrm/xfrm_state.c

diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 08564e0..ccfb172e 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -2620,7 +2620,7 @@ 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;