ipv4: annotate data races arount inet->min_ttl

No report yet from KCSAN, yet worth documenting the races.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index b297bb2..d5487c8 100644 (file)
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -1352,7 +1352,10 @@ static int do_ip_setsockopt(struct sock *sk, int level, int optname,
                        goto e_inval;
                if (val < 0 || val > 255)
                        goto e_inval;
-               inet->min_ttl = val;
+               /* tcp_v4_err() and tcp_v4_rcv() might read min_ttl
+                * while we are changint it.
+                */
+               WRITE_ONCE(inet->min_ttl, val);
                break;
 
        default:

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 2bdc32c..a9cbc8e 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -508,7 +508,8 @@ int tcp_v4_err(struct sk_buff *skb, u32 info)
        if (sk->sk_state == TCP_CLOSE)
                goto out;
 
-       if (unlikely(iph->ttl < inet_sk(sk)->min_ttl)) {
+       /* min_ttl can be changed concurrently from do_ip_setsockopt() */
+       if (unlikely(iph->ttl < READ_ONCE(inet_sk(sk)->min_ttl))) {
                __NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP);
                goto out;
        }
@@ -2068,7 +2069,9 @@ process:
                        return 0;
                }
        }
-       if (unlikely(iph->ttl < inet_sk(sk)->min_ttl)) {
+
+       /* min_ttl can be changed concurrently from do_ip_setsockopt() */
+       if (unlikely(iph->ttl < READ_ONCE(inet_sk(sk)->min_ttl))) {
                __NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP);
                goto discard_and_relse;
        }