net: fix NULL dereferences in check_peer_redir()
Gergely Kalman reported crashes in check_peer_redir().
It appears commit f39925dbde778 (ipv4: Cache learned redirect
information in inetpeer.) added a race, leading to possible NULL ptr
dereference.
Since we can now change dst neighbour, we should make sure a reader can
safely use a neighbour.
Add RCU protection to dst neighbour, and make sure check_peer_redir()
can be called safely by different cpus in parallel.
As neighbours are already freed after one RCU grace period, this patch
should not add typical RCU penalty (cache cold effects)
Many thanks to Gergely for providing a pretty report pointing to the
bug.
Reported-by: Gergely Kalman <synapse@hippy.csoma.elte.hu>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/dst.h b/include/net/dst.h
index 29e2557..13d507d 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -37,7 +37,7 @@
unsigned long _metrics;
unsigned long expires;
struct dst_entry *path;
- struct neighbour *_neighbour;
+ struct neighbour __rcu *_neighbour;
#ifdef CONFIG_XFRM
struct xfrm_state *xfrm;
#else
@@ -88,12 +88,17 @@
static inline struct neighbour *dst_get_neighbour(struct dst_entry *dst)
{
- return dst->_neighbour;
+ return rcu_dereference(dst->_neighbour);
+}
+
+static inline struct neighbour *dst_get_neighbour_raw(struct dst_entry *dst)
+{
+ return rcu_dereference_raw(dst->_neighbour);
}
static inline void dst_set_neighbour(struct dst_entry *dst, struct neighbour *neigh)
{
- dst->_neighbour = neigh;
+ rcu_assign_pointer(dst->_neighbour, neigh);
}
extern u32 *dst_cow_metrics_generic(struct dst_entry *dst, unsigned long old);
@@ -382,8 +387,12 @@
static inline void dst_confirm(struct dst_entry *dst)
{
if (dst) {
- struct neighbour *n = dst_get_neighbour(dst);
+ struct neighbour *n;
+
+ rcu_read_lock();
+ n = dst_get_neighbour(dst);
neigh_confirm(n);
+ rcu_read_unlock();
}
}
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index ccaaa85..77d3ede 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -204,9 +204,15 @@
skb = skb2;
}
+ rcu_read_lock();
neigh = dst_get_neighbour(dst);
- if (neigh)
- return neigh_output(neigh, skb);
+ if (neigh) {
+ int res = neigh_output(neigh, skb);
+
+ rcu_read_unlock();
+ return res;
+ }
+ rcu_read_unlock();
if (net_ratelimit())
printk(KERN_DEBUG "ip_finish_output2: No header cache and no neighbour!\n");
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 1730689f..6afc4eb 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1628,16 +1628,18 @@
{
struct rtable *rt = (struct rtable *) dst;
__be32 orig_gw = rt->rt_gateway;
- struct neighbour *n;
+ struct neighbour *n, *old_n;
dst_confirm(&rt->dst);
- neigh_release(dst_get_neighbour(&rt->dst));
- dst_set_neighbour(&rt->dst, NULL);
-
rt->rt_gateway = peer->redirect_learned.a4;
- rt_bind_neighbour(rt);
- n = dst_get_neighbour(&rt->dst);
+
+ n = ipv4_neigh_lookup(&rt->dst, &rt->rt_gateway);
+ if (IS_ERR(n))
+ return PTR_ERR(n);
+ old_n = xchg(&rt->dst._neighbour, n);
+ if (old_n)
+ neigh_release(old_n);
if (!n || !(n->nud_state & NUD_VALID)) {
if (n)
neigh_event_send(n, NULL);
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index a55500c..f012ebd 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -656,7 +656,7 @@
* layer address of our nexhop router
*/
- if (dst_get_neighbour(&rt->dst) == NULL)
+ if (dst_get_neighbour_raw(&rt->dst) == NULL)
ifa->flags &= ~IFA_F_OPTIMISTIC;
ifa->idev = idev;
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 54a4678..320d91d 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -1455,7 +1455,7 @@
RT6_TRACE("aging clone %p\n", rt);
return -1;
} else if ((rt->rt6i_flags & RTF_GATEWAY) &&
- (!(dst_get_neighbour(&rt->dst)->flags & NTF_ROUTER))) {
+ (!(dst_get_neighbour_raw(&rt->dst)->flags & NTF_ROUTER))) {
RT6_TRACE("purging route %p via non-router but gateway\n",
rt);
return -1;
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 32e5339..4c882cf 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -135,10 +135,15 @@
skb->len);
}
+ rcu_read_lock();
neigh = dst_get_neighbour(dst);
- if (neigh)
- return neigh_output(neigh, skb);
+ if (neigh) {
+ int res = neigh_output(neigh, skb);
+ rcu_read_unlock();
+ return res;
+ }
+ rcu_read_unlock();
IP6_INC_STATS_BH(dev_net(dst->dev),
ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
kfree_skb(skb);
@@ -975,12 +980,14 @@
* dst entry and replace it instead with the
* dst entry of the nexthop router
*/
+ rcu_read_lock();
n = dst_get_neighbour(*dst);
if (n && !(n->nud_state & NUD_VALID)) {
struct inet6_ifaddr *ifp;
struct flowi6 fl_gw6;
int redirect;
+ rcu_read_unlock();
ifp = ipv6_get_ifaddr(net, &fl6->saddr,
(*dst)->dev, 1);
@@ -1000,6 +1007,8 @@
if ((err = (*dst)->error))
goto out_err_release;
}
+ } else {
+ rcu_read_unlock();
}
#endif
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index e8987da..9e69eb0 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -364,7 +364,7 @@
#ifdef CONFIG_IPV6_ROUTER_PREF
static void rt6_probe(struct rt6_info *rt)
{
- struct neighbour *neigh = rt ? dst_get_neighbour(&rt->dst) : NULL;
+ struct neighbour *neigh;
/*
* Okay, this does not seem to be appropriate
* for now, however, we need to check if it
@@ -373,8 +373,10 @@
* Router Reachability Probe MUST be rate-limited
* to no more than one per minute.
*/
+ rcu_read_lock();
+ neigh = rt ? dst_get_neighbour(&rt->dst) : NULL;
if (!neigh || (neigh->nud_state & NUD_VALID))
- return;
+ goto out;
read_lock_bh(&neigh->lock);
if (!(neigh->nud_state & NUD_VALID) &&
time_after(jiffies, neigh->updated + rt->rt6i_idev->cnf.rtr_probe_interval)) {
@@ -387,8 +389,11 @@
target = (struct in6_addr *)&neigh->primary_key;
addrconf_addr_solict_mult(target, &mcaddr);
ndisc_send_ns(rt->rt6i_dev, NULL, target, &mcaddr, NULL);
- } else
+ } else {
read_unlock_bh(&neigh->lock);
+ }
+out:
+ rcu_read_unlock();
}
#else
static inline void rt6_probe(struct rt6_info *rt)
@@ -412,8 +417,11 @@
static inline int rt6_check_neigh(struct rt6_info *rt)
{
- struct neighbour *neigh = dst_get_neighbour(&rt->dst);
+ struct neighbour *neigh;
int m;
+
+ rcu_read_lock();
+ neigh = dst_get_neighbour(&rt->dst);
if (rt->rt6i_flags & RTF_NONEXTHOP ||
!(rt->rt6i_flags & RTF_GATEWAY))
m = 1;
@@ -430,6 +438,7 @@
read_unlock_bh(&neigh->lock);
} else
m = 0;
+ rcu_read_unlock();
return m;
}
@@ -769,7 +778,7 @@
rt->rt6i_dst.plen = 128;
rt->rt6i_flags |= RTF_CACHE;
rt->dst.flags |= DST_HOST;
- dst_set_neighbour(&rt->dst, neigh_clone(dst_get_neighbour(&ort->dst)));
+ dst_set_neighbour(&rt->dst, neigh_clone(dst_get_neighbour_raw(&ort->dst)));
}
return rt;
}
@@ -803,7 +812,7 @@
dst_hold(&rt->dst);
read_unlock_bh(&table->tb6_lock);
- if (!dst_get_neighbour(&rt->dst) && !(rt->rt6i_flags & RTF_NONEXTHOP))
+ if (!dst_get_neighbour_raw(&rt->dst) && !(rt->rt6i_flags & RTF_NONEXTHOP))
nrt = rt6_alloc_cow(rt, &fl6->daddr, &fl6->saddr);
else if (!(rt->dst.flags & DST_HOST))
nrt = rt6_alloc_clone(rt, &fl6->daddr);
@@ -1587,7 +1596,7 @@
dst_confirm(&rt->dst);
/* Duplicate redirect: silently ignore. */
- if (neigh == dst_get_neighbour(&rt->dst))
+ if (neigh == dst_get_neighbour_raw(&rt->dst))
goto out;
nrt = ip6_rt_copy(rt, dest);
@@ -1682,7 +1691,7 @@
1. It is connected route. Action: COW
2. It is gatewayed route or NONEXTHOP route. Action: clone it.
*/
- if (!dst_get_neighbour(&rt->dst) && !(rt->rt6i_flags & RTF_NONEXTHOP))
+ if (!dst_get_neighbour_raw(&rt->dst) && !(rt->rt6i_flags & RTF_NONEXTHOP))
nrt = rt6_alloc_cow(rt, daddr, saddr);
else
nrt = rt6_alloc_clone(rt, daddr);
@@ -2326,6 +2335,7 @@
struct nlmsghdr *nlh;
long expires;
u32 table;
+ struct neighbour *n;
if (prefix) { /* user wants prefix routes only */
if (!(rt->rt6i_flags & RTF_PREFIX_RT)) {
@@ -2414,8 +2424,11 @@
if (rtnetlink_put_metrics(skb, dst_metrics_ptr(&rt->dst)) < 0)
goto nla_put_failure;
- if (dst_get_neighbour(&rt->dst))
- NLA_PUT(skb, RTA_GATEWAY, 16, &dst_get_neighbour(&rt->dst)->primary_key);
+ rcu_read_lock();
+ n = dst_get_neighbour(&rt->dst);
+ if (n)
+ NLA_PUT(skb, RTA_GATEWAY, 16, &n->primary_key);
+ rcu_read_unlock();
if (rt->dst.dev)
NLA_PUT_U32(skb, RTA_OIF, rt->rt6i_dev->ifindex);
@@ -2608,12 +2621,14 @@
#else
seq_puts(m, "00000000000000000000000000000000 00 ");
#endif
+ rcu_read_lock();
n = dst_get_neighbour(&rt->dst);
if (n) {
seq_printf(m, "%pi6", n->primary_key);
} else {
seq_puts(m, "00000000000000000000000000000000");
}
+ rcu_read_unlock();
seq_printf(m, " %08x %08x %08x %08x %8s\n",
rt->rt6i_metric, atomic_read(&rt->dst.__refcnt),
rt->dst.__use, rt->rt6i_flags,
