From: Eric Dumazet <edumazet@google.com>
Date: Tue, 5 Nov 2019 14:11:51 -0800
Subject: net: avoid potential false sharing in neighbor related code
Patch-mainline: v5.5-rc1
Git-commit: 25c7a6d1f90e208ec27ca854b1381ed39842ec57
References: bsc#1154353
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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
include/net/arp.h | 4 ++--
include/net/ndisc.h | 8 ++++----
include/net/sock.h | 12 ++++++------
3 files changed, 12 insertions(+), 12 deletions(-)
--- a/include/net/arp.h
+++ b/include/net/arp.h
@@ -57,8 +57,8 @@ static inline void __ipv4_confirm_neigh(
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();
}
--- a/include/net/ndisc.h
+++ b/include/net/ndisc.h
@@ -413,8 +413,8 @@ static inline void __ipv6_confirm_neigh(
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();
}
@@ -430,8 +430,8 @@ static inline void __ipv6_confirm_neigh_
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();
}
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1940,8 +1940,8 @@ struct dst_entry *sk_dst_check(struct so
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(st
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);
}
}