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authorMartin KaFai Lau <kafai@fb.com>2015-09-16 00:30:07 +0300
committerDavid S. Miller <davem@davemloft.net>2015-09-16 00:53:05 +0300
commitcdf3464e6c6bd764277cbbe992cd12da735b92fb (patch)
tree53e75a7f94aba7ced57ae7f2b527bce0d463a629 /net/ipv6/ip6_tunnel.c
parentf230d1e891ba1da5953460516960894154f265db (diff)
downloadlinux-cdf3464e6c6bd764277cbbe992cd12da735b92fb.tar.xz
ipv6: Fix dst_entry refcnt bugs in ip6_tunnel
Problems in the current dst_entry cache in the ip6_tunnel: 1. ip6_tnl_dst_set is racy. There is no lock to protect it: - One major problem is that the dst refcnt gets messed up. F.e. the same dst_cache can be released multiple times and then triggering the infamous dst refcnt < 0 warning message. - Another issue is the inconsistency between dst_cache and dst_cookie. It can be reproduced by adding and removing the ip6gre tunnel while running a super_netperf TCP_CRR test. 2. ip6_tnl_dst_get does not take the dst refcnt before returning the dst. This patch: 1. Create a percpu dst_entry cache in ip6_tnl 2. Use a spinlock to protect the dst_cache operations 3. ip6_tnl_dst_get always takes the dst refcnt before returning Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6/ip6_tunnel.c')
-rw-r--r--net/ipv6/ip6_tunnel.c122
1 files changed, 92 insertions, 30 deletions
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 599b0b419fbc..851cf6d1eb45 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -126,37 +126,90 @@ static struct net_device_stats *ip6_get_stats(struct net_device *dev)
* Locking : hash tables are protected by RCU and RTNL
*/
-struct dst_entry *ip6_tnl_dst_get(struct ip6_tnl *t)
+static void __ip6_tnl_per_cpu_dst_set(struct ip6_tnl_dst *idst,
+ struct dst_entry *dst)
{
- struct dst_entry *dst = t->dst_cache;
-
- if (dst && dst->obsolete &&
- !dst->ops->check(dst, t->dst_cookie)) {
- t->dst_cache = NULL;
- dst_release(dst);
- return NULL;
+ dst_release(idst->dst);
+ if (dst) {
+ dst_hold(dst);
+ idst->cookie = rt6_get_cookie((struct rt6_info *)dst);
+ } else {
+ idst->cookie = 0;
}
+ idst->dst = dst;
+}
+
+static void ip6_tnl_per_cpu_dst_set(struct ip6_tnl_dst *idst,
+ struct dst_entry *dst)
+{
+ spin_lock_bh(&idst->lock);
+ __ip6_tnl_per_cpu_dst_set(idst, dst);
+ spin_unlock_bh(&idst->lock);
+}
+
+struct dst_entry *ip6_tnl_dst_get(struct ip6_tnl *t)
+{
+ struct ip6_tnl_dst *idst;
+ struct dst_entry *dst;
+
+ idst = raw_cpu_ptr(t->dst_cache);
+ spin_lock_bh(&idst->lock);
+ dst = idst->dst;
+ if (dst) {
+ if (!dst->obsolete || dst->ops->check(dst, idst->cookie)) {
+ dst_hold(idst->dst);
+ } else {
+ __ip6_tnl_per_cpu_dst_set(idst, NULL);
+ dst = NULL;
+ }
+ }
+ spin_unlock_bh(&idst->lock);
return dst;
}
EXPORT_SYMBOL_GPL(ip6_tnl_dst_get);
void ip6_tnl_dst_reset(struct ip6_tnl *t)
{
- dst_release(t->dst_cache);
- t->dst_cache = NULL;
+ int i;
+
+ for_each_possible_cpu(i)
+ ip6_tnl_per_cpu_dst_set(raw_cpu_ptr(t->dst_cache), NULL);
}
EXPORT_SYMBOL_GPL(ip6_tnl_dst_reset);
void ip6_tnl_dst_set(struct ip6_tnl *t, struct dst_entry *dst)
{
- struct rt6_info *rt = (struct rt6_info *) dst;
- t->dst_cookie = rt6_get_cookie(rt);
- dst_release(t->dst_cache);
- t->dst_cache = dst;
+ ip6_tnl_per_cpu_dst_set(raw_cpu_ptr(t->dst_cache), dst);
+
}
EXPORT_SYMBOL_GPL(ip6_tnl_dst_set);
+void ip6_tnl_dst_destroy(struct ip6_tnl *t)
+{
+ if (!t->dst_cache)
+ return;
+
+ ip6_tnl_dst_reset(t);
+ free_percpu(t->dst_cache);
+}
+EXPORT_SYMBOL_GPL(ip6_tnl_dst_destroy);
+
+int ip6_tnl_dst_init(struct ip6_tnl *t)
+{
+ int i;
+
+ t->dst_cache = alloc_percpu(struct ip6_tnl_dst);
+ if (!t->dst_cache)
+ return -ENOMEM;
+
+ for_each_possible_cpu(i)
+ spin_lock_init(&per_cpu_ptr(t->dst_cache, i)->lock);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(ip6_tnl_dst_init);
+
/**
* ip6_tnl_lookup - fetch tunnel matching the end-point addresses
* @remote: the address of the tunnel exit-point
@@ -271,6 +324,9 @@ ip6_tnl_unlink(struct ip6_tnl_net *ip6n, struct ip6_tnl *t)
static void ip6_dev_free(struct net_device *dev)
{
+ struct ip6_tnl *t = netdev_priv(dev);
+
+ ip6_tnl_dst_destroy(t);
free_percpu(dev->tstats);
free_netdev(dev);
}
@@ -1016,17 +1072,17 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
goto tx_err_link_failure;
if (!dst) {
- ndst = ip6_route_output(net, NULL, fl6);
+ dst = ip6_route_output(net, NULL, fl6);
- if (ndst->error)
+ if (dst->error)
goto tx_err_link_failure;
- ndst = xfrm_lookup(net, ndst, flowi6_to_flowi(fl6), NULL, 0);
- if (IS_ERR(ndst)) {
- err = PTR_ERR(ndst);
- ndst = NULL;
+ dst = xfrm_lookup(net, dst, flowi6_to_flowi(fl6), NULL, 0);
+ if (IS_ERR(dst)) {
+ err = PTR_ERR(dst);
+ dst = NULL;
goto tx_err_link_failure;
}
- dst = ndst;
+ ndst = dst;
}
tdev = dst->dev;
@@ -1072,12 +1128,11 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
consume_skb(skb);
skb = new_skb;
}
- if (fl6->flowi6_mark) {
- skb_dst_set(skb, dst);
- ndst = NULL;
- } else {
- skb_dst_set_noref(skb, dst);
- }
+
+ if (!fl6->flowi6_mark && ndst)
+ ip6_tnl_dst_set(t, ndst);
+ skb_dst_set(skb, dst);
+
skb->transport_header = skb->network_header;
proto = fl6->flowi6_proto;
@@ -1101,14 +1156,12 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
ipv6h->saddr = fl6->saddr;
ipv6h->daddr = fl6->daddr;
ip6tunnel_xmit(NULL, skb, dev);
- if (ndst)
- ip6_tnl_dst_set(t, ndst);
return 0;
tx_err_link_failure:
stats->tx_carrier_errors++;
dst_link_failure(skb);
tx_err_dst_release:
- dst_release(ndst);
+ dst_release(dst);
return err;
}
@@ -1573,12 +1626,21 @@ static inline int
ip6_tnl_dev_init_gen(struct net_device *dev)
{
struct ip6_tnl *t = netdev_priv(dev);
+ int ret;
t->dev = dev;
t->net = dev_net(dev);
dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
if (!dev->tstats)
return -ENOMEM;
+
+ ret = ip6_tnl_dst_init(t);
+ if (ret) {
+ free_percpu(dev->tstats);
+ dev->tstats = NULL;
+ return ret;
+ }
+
return 0;
}