[PATCH AUTOSEL 5.4 237/350] net: avoid potential false sharing in neighbor related code
From: Sasha Levin <sashal@kernel.org>
Date: 2019-12-10 21:21:56
Also in:
lkml, stable
Subsystem:
networking [general], networking [ipv4/ipv6], networking [sockets], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, David Ahern, Ido Schimmel, Kuniyuki Iwashima, Willem de Bruijn, Linus Torvalds
From: Eric Dumazet <edumazet@google.com> [ Upstream commit 25c7a6d1f90e208ec27ca854b1381ed39842ec57 ] There are common instances of the following construct : if (n->confirmed != now) n->confirmed = now; A C compiler could legally remove the conditional. Use READ_ONCE()/WRITE_ONCE() to avoid this problem. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org> --- include/net/arp.h | 4 ++-- include/net/ndisc.h | 8 ++++---- include/net/sock.h | 12 ++++++------ 3 files changed, 12 insertions(+), 12 deletions(-)
diff --git a/include/net/arp.h b/include/net/arp.h
index c8f580a0e6b1f..4950191f6b2bf 100644
--- a/include/net/arp.h
+++ b/include/net/arp.h@@ -57,8 +57,8 @@ static inline void __ipv4_confirm_neigh(struct net_device *dev, u32 key) unsigned long now = jiffies; /* avoid dirtying neighbour */ - if (n->confirmed != now) - n->confirmed = now; + if (READ_ONCE(n->confirmed) != now) + WRITE_ONCE(n->confirmed, now); } rcu_read_unlock_bh(); }
diff --git a/include/net/ndisc.h b/include/net/ndisc.h
index b2f715ca05672..b5ebeb3b0de0e 100644
--- a/include/net/ndisc.h
+++ b/include/net/ndisc.h@@ -414,8 +414,8 @@ static inline void __ipv6_confirm_neigh(struct net_device *dev, unsigned long now = jiffies; /* avoid dirtying neighbour */ - if (n->confirmed != now) - n->confirmed = now; + if (READ_ONCE(n->confirmed) != now) + WRITE_ONCE(n->confirmed, now); } rcu_read_unlock_bh(); }
@@ -431,8 +431,8 @@ static inline void __ipv6_confirm_neigh_stub(struct net_device *dev, unsigned long now = jiffies; /* avoid dirtying neighbour */ - if (n->confirmed != now) - n->confirmed = now; + if (READ_ONCE(n->confirmed) != now) + WRITE_ONCE(n->confirmed, now); } rcu_read_unlock_bh(); }
diff --git a/include/net/sock.h b/include/net/sock.h
index 718e62fbe869d..013396e50b91f 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h@@ -1940,8 +1940,8 @@ struct dst_entry *sk_dst_check(struct sock *sk, u32 cookie); static inline void sk_dst_confirm(struct sock *sk) { - if (!sk->sk_dst_pending_confirm) - sk->sk_dst_pending_confirm = 1; + if (!READ_ONCE(sk->sk_dst_pending_confirm)) + WRITE_ONCE(sk->sk_dst_pending_confirm, 1); } static inline void sock_confirm_neigh(struct sk_buff *skb, struct neighbour *n)
@@ -1951,10 +1951,10 @@ static inline void sock_confirm_neigh(struct sk_buff *skb, struct neighbour *n) unsigned long now = jiffies; /* avoid dirtying neighbour */ - if (n->confirmed != now) - n->confirmed = now; - if (sk && sk->sk_dst_pending_confirm) - sk->sk_dst_pending_confirm = 0; + if (READ_ONCE(n->confirmed) != now) + WRITE_ONCE(n->confirmed, now); + if (sk && READ_ONCE(sk->sk_dst_pending_confirm)) + WRITE_ONCE(sk->sk_dst_pending_confirm, 0); } }
--
2.20.1