From 00ca9c5b2b11d44eaf20a4b647efc999734323ec Mon Sep 17 00:00:00 2001 From: Christoph Paasch Date: Tue, 21 Jan 2014 13:30:26 +0100 Subject: [PATCH] tcp: metrics: Fix rcu-race when deleting multiple entries In bbf852b96ebdc6d1 I introduced the tmlist, which allows to delete multiple entries from the cache that match a specified destination if no source-IP is specified. However, as the cache is an RCU-list, we should not create this tmlist, as it will change the tcpm_next pointer of the element that will be deleted and so a thread iterating over the cache's entries while holding the RCU-lock might get "redirected" to this tmlist. This patch fixes this, by reverting back to the old behavior prior to bbf852b96ebdc6d1, which means that we simply change the tcpm_next pointer of the previous element (pp) to jump over the one we are deleting. The difference is that we call kfree_rcu() directly on the cache entry, which allows us to delete multiple entries from the list. Fixes: bbf852b96ebdc6d1 (tcp: metrics: Delete all entries matching a certain destination) Signed-off-by: Christoph Paasch Signed-off-by: David S. Miller --- net/ipv4/tcp_metrics.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c index fa950941de65..9ae48b4a37d1 100644 --- a/net/ipv4/tcp_metrics.c +++ b/net/ipv4/tcp_metrics.c @@ -1019,13 +1019,13 @@ static int tcp_metrics_flush_all(struct net *net) static int tcp_metrics_nl_cmd_del(struct sk_buff *skb, struct genl_info *info) { struct tcpm_hash_bucket *hb; - struct tcp_metrics_block *tm, *tmlist = NULL; + struct tcp_metrics_block *tm; struct tcp_metrics_block __rcu **pp; struct inetpeer_addr saddr, daddr; unsigned int hash; struct net *net = genl_info_net(info); int ret; - bool src = true; + bool src = true, found = false; ret = parse_nl_addr(info, &daddr, &hash, 1); if (ret < 0) @@ -1044,19 +1044,15 @@ static int tcp_metrics_nl_cmd_del(struct sk_buff *skb, struct genl_info *info) if (addr_same(&tm->tcpm_daddr, &daddr) && (!src || addr_same(&tm->tcpm_saddr, &saddr))) { *pp = tm->tcpm_next; - tm->tcpm_next = tmlist; - tmlist = tm; + kfree_rcu(tm, rcu_head); + found = true; } else { pp = &tm->tcpm_next; } } spin_unlock_bh(&tcp_metrics_lock); - if (!tmlist) + if (!found) return -ESRCH; - for (tm = tmlist; tm; tm = tmlist) { - tmlist = tm->tcpm_next; - kfree_rcu(tm, rcu_head); - } return 0; } -- 2.30.2