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Commit cdf3464e authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by David S. Miller
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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: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f230d1e8
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Inline Side-by-side
Showing with 123 additions and 48 deletions
include/net/ip6_tunnel.h
View file @ cdf3464e
......@@ -32,6 +32,12 @@ struct __ip6_tnl_parm {
__be32 o_key;
};
struct ip6_tnl_dst {
spinlock_t lock;
struct dst_entry *dst;
u32 cookie;
};
/* IPv6 tunnel */
struct ip6_tnl {
struct ip6_tnl __rcu *next; /* next tunnel in list */
......@@ -39,8 +45,7 @@ struct ip6_tnl {
struct net *net; /* netns for packet i/o */
struct __ip6_tnl_parm parms; /* tunnel configuration parameters */
struct flowi fl; /* flowi template for xmit */
struct dst_entry *dst_cache; /* cached dst */
u32 dst_cookie;
struct ip6_tnl_dst __percpu *dst_cache; /* cached dst */
int err_count;
unsigned long err_time;
......@@ -61,6 +66,8 @@ struct ipv6_tlv_tnl_enc_lim {
} __packed;
struct dst_entry *ip6_tnl_dst_get(struct ip6_tnl *t);
int ip6_tnl_dst_init(struct ip6_tnl *t);
void ip6_tnl_dst_destroy(struct ip6_tnl *t);
void ip6_tnl_dst_reset(struct ip6_tnl *t);
void ip6_tnl_dst_set(struct ip6_tnl *t, struct dst_entry *dst);
int ip6_tnl_rcv_ctl(struct ip6_tnl *t, const struct in6_addr *laddr,
......
net/ipv6/ip6_gre.c
View file @ cdf3464e
......@@ -637,17 +637,17 @@ static netdev_tx_t ip6gre_xmit2(struct sk_buff *skb,
dst = ip6_tnl_dst_get(tunnel);
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;
......@@ -702,12 +702,9 @@ static netdev_tx_t ip6gre_xmit2(struct sk_buff *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(tunnel, ndst);
skb_dst_set(skb, dst);
proto = NEXTHDR_GRE;
if (encap_limit >= 0) {
......@@ -762,14 +759,12 @@ static netdev_tx_t ip6gre_xmit2(struct sk_buff *skb,
skb_set_inner_protocol(skb, protocol);
ip6tunnel_xmit(NULL, skb, dev);
if (ndst)
ip6_tnl_dst_set(tunnel, 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;
}
......@@ -1223,6 +1218,9 @@ static const struct net_device_ops ip6gre_netdev_ops = {
static void ip6gre_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);
}
......@@ -1248,6 +1246,7 @@ static void ip6gre_tunnel_setup(struct net_device *dev)
static int ip6gre_tunnel_init_common(struct net_device *dev)
{
struct ip6_tnl *tunnel;
int ret;
tunnel = netdev_priv(dev);
......@@ -1259,6 +1258,13 @@ static int ip6gre_tunnel_init_common(struct net_device *dev)
if (!dev->tstats)
return -ENOMEM;
ret = ip6_tnl_dst_init(tunnel);
if (ret) {
free_percpu(dev->tstats);
dev->tstats = NULL;
return ret;
}
return 0;
}
......
net/ipv6/ip6_tunnel.c
View file @ cdf3464e
......@@ -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;
}
......
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