diff options
| author | Pablo Neira Ayuso <pablo@netfilter.org> | 2006-09-20 12:01:06 -0700 |
|---|---|---|
| committer | David S. Miller <davem@sunset.davemloft.net> | 2006-09-22 15:19:54 -0700 |
| commit | 5251e2d2125407bbff0c39394a4011be9ed8b5d0 (patch) | |
| tree | 3dda0aeb90d80a2ddd0e7a4215bfe9eaa8209033 /net/ipv4 | |
| parent | 01f348484dd8509254d045e3ad49029716eca6a1 (diff) | |
[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 <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/netfilter/ip_conntrack_core.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/net/ipv4/netfilter/ip_conntrack_core.c b/net/ipv4/netfilter/ip_conntrack_core.c index 2568d480e9a..422a662194c 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; } |