From 5251e2d2125407bbff0c39394a4011be9ed8b5d0 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Wed, 20 Sep 2006 12:01:06 -0700 Subject: [NETFILTER]: conntrack: fix race condition in early_drop On SMP environments the maximum number of conntracks can be overpassed under heavy stress situations due to an existing race condition. CPU A CPU B atomic_read() ... early_drop() ... ... atomic_read() allocate conntrack allocate conntrack atomic_inc() atomic_inc() This patch moves the counter incrementation before the early drop stage. Signed-off-by: Pablo Neira Ayuso Signed-off-by: Patrick McHardy Signed-off-by: David S. Miller --- net/ipv4/netfilter/ip_conntrack_core.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/netfilter/ip_conntrack_core.c b/net/ipv4/netfilter/ip_conntrack_core.c index 2568d480e9a9..422a662194cc 100644 --- a/net/ipv4/netfilter/ip_conntrack_core.c +++ b/net/ipv4/netfilter/ip_conntrack_core.c @@ -622,11 +622,15 @@ struct ip_conntrack *ip_conntrack_alloc(struct ip_conntrack_tuple *orig, ip_conntrack_hash_rnd_initted = 1; } + /* We don't want any race condition at early drop stage */ + atomic_inc(&ip_conntrack_count); + if (ip_conntrack_max - && atomic_read(&ip_conntrack_count) >= ip_conntrack_max) { + && atomic_read(&ip_conntrack_count) > ip_conntrack_max) { unsigned int hash = hash_conntrack(orig); /* Try dropping from this hash chain. */ if (!early_drop(&ip_conntrack_hash[hash])) { + atomic_dec(&ip_conntrack_count); if (net_ratelimit()) printk(KERN_WARNING "ip_conntrack: table full, dropping" @@ -638,6 +642,7 @@ struct ip_conntrack *ip_conntrack_alloc(struct ip_conntrack_tuple *orig, conntrack = kmem_cache_alloc(ip_conntrack_cachep, GFP_ATOMIC); if (!conntrack) { DEBUGP("Can't allocate conntrack.\n"); + atomic_dec(&ip_conntrack_count); return ERR_PTR(-ENOMEM); } @@ -651,8 +656,6 @@ struct ip_conntrack *ip_conntrack_alloc(struct ip_conntrack_tuple *orig, conntrack->timeout.data = (unsigned long)conntrack; conntrack->timeout.function = death_by_timeout; - atomic_inc(&ip_conntrack_count); - return conntrack; } -- cgit