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Subject[PATCH 4.4 04/22] ip_tunnel: replace dst_cache with generic implementation
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paolo Abeni <pabeni@redhat.com>

commit e09acddf873bf775b208b452a4c3a3fd26fa9427 upstream.

The current ip_tunnel cache implementation is prone to a race
that will cause the wrong dst to be cached on cuncurrent dst cache
miss and ip tunnel update via netlink.

Replacing with the generic implementation fix the issue.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Suggested-and-acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/net/ip_tunnels.h | 9 +----
net/ipv4/Kconfig | 1
net/ipv4/ip_tunnel.c | 78 +++++++----------------------------------------
net/ipv6/sit.c | 17 +++++-----
4 files changed, 25 insertions(+), 80 deletions(-)

--- a/include/net/ip_tunnels.h
+++ b/include/net/ip_tunnels.h
@@ -13,6 +13,7 @@
#include <net/netns/generic.h>
#include <net/rtnetlink.h>
#include <net/lwtunnel.h>
+#include <net/dst_cache.h>

#if IS_ENABLED(CONFIG_IPV6)
#include <net/ipv6.h>
@@ -85,11 +86,6 @@ struct ip_tunnel_prl_entry {
struct rcu_head rcu_head;
};

-struct ip_tunnel_dst {
- struct dst_entry __rcu *dst;
- __be32 saddr;
-};
-
struct metadata_dst;

struct ip_tunnel {
@@ -108,7 +104,7 @@ struct ip_tunnel {
int tun_hlen; /* Precalculated header length */
int mlink;

- struct ip_tunnel_dst __percpu *dst_cache;
+ struct dst_cache dst_cache;

struct ip_tunnel_parm parms;

@@ -248,7 +244,6 @@ int ip_tunnel_changelink(struct net_devi
int ip_tunnel_newlink(struct net_device *dev, struct nlattr *tb[],
struct ip_tunnel_parm *p);
void ip_tunnel_setup(struct net_device *dev, int net_id);
-void ip_tunnel_dst_reset_all(struct ip_tunnel *t);
int ip_tunnel_encap_setup(struct ip_tunnel *t,
struct ip_tunnel_encap *ipencap);

--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -186,6 +186,7 @@ config NET_IPGRE_DEMUX

config NET_IP_TUNNEL
tristate
+ select DST_CACHE
default n

config NET_IPGRE
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -69,61 +69,6 @@ static unsigned int ip_tunnel_hash(__be3
IP_TNL_HASH_BITS);
}

-static void __tunnel_dst_set(struct ip_tunnel_dst *idst,
- struct dst_entry *dst, __be32 saddr)
-{
- struct dst_entry *old_dst;
-
- dst_clone(dst);
- old_dst = xchg((__force struct dst_entry **)&idst->dst, dst);
- dst_release(old_dst);
- idst->saddr = saddr;
-}
-
-static noinline void tunnel_dst_set(struct ip_tunnel *t,
- struct dst_entry *dst, __be32 saddr)
-{
- __tunnel_dst_set(raw_cpu_ptr(t->dst_cache), dst, saddr);
-}
-
-static void tunnel_dst_reset(struct ip_tunnel *t)
-{
- tunnel_dst_set(t, NULL, 0);
-}
-
-void ip_tunnel_dst_reset_all(struct ip_tunnel *t)
-{
- int i;
-
- for_each_possible_cpu(i)
- __tunnel_dst_set(per_cpu_ptr(t->dst_cache, i), NULL, 0);
-}
-EXPORT_SYMBOL(ip_tunnel_dst_reset_all);
-
-static struct rtable *tunnel_rtable_get(struct ip_tunnel *t,
- u32 cookie, __be32 *saddr)
-{
- struct ip_tunnel_dst *idst;
- struct dst_entry *dst;
-
- rcu_read_lock();
- idst = raw_cpu_ptr(t->dst_cache);
- dst = rcu_dereference(idst->dst);
- if (dst && !atomic_inc_not_zero(&dst->__refcnt))
- dst = NULL;
- if (dst) {
- if (!dst->obsolete || dst->ops->check(dst, cookie)) {
- *saddr = idst->saddr;
- } else {
- tunnel_dst_reset(t);
- dst_release(dst);
- dst = NULL;
- }
- }
- rcu_read_unlock();
- return (struct rtable *)dst;
-}
-
static bool ip_tunnel_key_match(const struct ip_tunnel_parm *p,
__be16 flags, __be32 key)
{
@@ -382,7 +327,8 @@ static int ip_tunnel_bind_dev(struct net

if (!IS_ERR(rt)) {
tdev = rt->dst.dev;
- tunnel_dst_set(tunnel, &rt->dst, fl4.saddr);
+ dst_cache_set_ip4(&tunnel->dst_cache, &rt->dst,
+ fl4.saddr);
ip_rt_put(rt);
}
if (dev->type != ARPHRD_ETHER)
@@ -733,7 +679,8 @@ void ip_tunnel_xmit(struct sk_buff *skb,
if (ip_tunnel_encap(skb, tunnel, &protocol, &fl4) < 0)
goto tx_error;

- rt = connected ? tunnel_rtable_get(tunnel, 0, &fl4.saddr) : NULL;
+ rt = connected ? dst_cache_get_ip4(&tunnel->dst_cache, &fl4.saddr) :
+ NULL;

if (!rt) {
rt = ip_route_output_key(tunnel->net, &fl4);
@@ -743,7 +690,8 @@ void ip_tunnel_xmit(struct sk_buff *skb,
goto tx_error;
}
if (connected)
- tunnel_dst_set(tunnel, &rt->dst, fl4.saddr);
+ dst_cache_set_ip4(&tunnel->dst_cache, &rt->dst,
+ fl4.saddr);
}

if (rt->dst.dev == dev) {
@@ -841,7 +789,7 @@ static void ip_tunnel_update(struct ip_t
if (set_mtu)
dev->mtu = mtu;
}
- ip_tunnel_dst_reset_all(t);
+ dst_cache_reset(&t->dst_cache);
netdev_state_change(dev);
}

@@ -980,7 +928,7 @@ static void ip_tunnel_dev_free(struct ne
struct ip_tunnel *tunnel = netdev_priv(dev);

gro_cells_destroy(&tunnel->gro_cells);
- free_percpu(tunnel->dst_cache);
+ dst_cache_destroy(&tunnel->dst_cache);
free_percpu(dev->tstats);
free_netdev(dev);
}
@@ -1174,15 +1122,15 @@ int ip_tunnel_init(struct net_device *de
if (!dev->tstats)
return -ENOMEM;

- tunnel->dst_cache = alloc_percpu(struct ip_tunnel_dst);
- if (!tunnel->dst_cache) {
+ err = dst_cache_init(&tunnel->dst_cache, GFP_KERNEL);
+ if (err) {
free_percpu(dev->tstats);
- return -ENOMEM;
+ return err;
}

err = gro_cells_init(&tunnel->gro_cells, dev);
if (err) {
- free_percpu(tunnel->dst_cache);
+ dst_cache_destroy(&tunnel->dst_cache);
free_percpu(dev->tstats);
return err;
}
@@ -1212,7 +1160,7 @@ void ip_tunnel_uninit(struct net_device
if (itn->fb_tunnel_dev != dev)
ip_tunnel_del(itn, netdev_priv(dev));

- ip_tunnel_dst_reset_all(tunnel);
+ dst_cache_reset(&tunnel->dst_cache);
}
EXPORT_SYMBOL_GPL(ip_tunnel_uninit);

--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -475,7 +475,7 @@ static void ipip6_tunnel_uninit(struct n
ipip6_tunnel_unlink(sitn, tunnel);
ipip6_tunnel_del_prl(tunnel, NULL);
}
- ip_tunnel_dst_reset_all(tunnel);
+ dst_cache_reset(&tunnel->dst_cache);
dev_put(dev);
}

@@ -1098,7 +1098,7 @@ static void ipip6_tunnel_update(struct i
t->parms.link = p->link;
ipip6_tunnel_bind_dev(t->dev);
}
- ip_tunnel_dst_reset_all(t);
+ dst_cache_reset(&t->dst_cache);
netdev_state_change(t->dev);
}

@@ -1129,7 +1129,7 @@ static int ipip6_tunnel_update_6rd(struc
t->ip6rd.relay_prefix = relay_prefix;
t->ip6rd.prefixlen = ip6rd->prefixlen;
t->ip6rd.relay_prefixlen = ip6rd->relay_prefixlen;
- ip_tunnel_dst_reset_all(t);
+ dst_cache_reset(&t->dst_cache);
netdev_state_change(t->dev);
return 0;
}
@@ -1283,7 +1283,7 @@ ipip6_tunnel_ioctl(struct net_device *de
err = ipip6_tunnel_add_prl(t, &prl, cmd == SIOCCHGPRL);
break;
}
- ip_tunnel_dst_reset_all(t);
+ dst_cache_reset(&t->dst_cache);
netdev_state_change(dev);
break;

@@ -1344,7 +1344,7 @@ static void ipip6_dev_free(struct net_de
{
struct ip_tunnel *tunnel = netdev_priv(dev);

- free_percpu(tunnel->dst_cache);
+ dst_cache_destroy(&tunnel->dst_cache);
free_percpu(dev->tstats);
free_netdev(dev);
}
@@ -1377,6 +1377,7 @@ static void ipip6_tunnel_setup(struct ne
static int ipip6_tunnel_init(struct net_device *dev)
{
struct ip_tunnel *tunnel = netdev_priv(dev);
+ int err;

tunnel->dev = dev;
tunnel->net = dev_net(dev);
@@ -1387,11 +1388,11 @@ static int ipip6_tunnel_init(struct net_
if (!dev->tstats)
return -ENOMEM;

- tunnel->dst_cache = alloc_percpu(struct ip_tunnel_dst);
- if (!tunnel->dst_cache) {
+ err = dst_cache_init(&tunnel->dst_cache, GFP_KERNEL);
+ if (err) {
free_percpu(dev->tstats);
dev->tstats = NULL;
- return -ENOMEM;
+ return err;
}

return 0;

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