ipv6: add rcu grace period before freeing fib6_node
[ Upstream commit c5cff8561d2d0006e972bd114afd51f082fee77c ]
We currently keep rt->rt6i_node pointing to the fib6_node for the route.
And some functions make use of this pointer to dereference the fib6_node
from rt structure, e.g. rt6_check(). However, as there is neither
refcount nor rcu taken when dereferencing rt->rt6i_node, it could
potentially cause crashes as rt->rt6i_node could be set to NULL by other
CPUs when doing a route deletion.
This patch introduces an rcu grace period before freeing fib6_node and
makes sure the functions that dereference it takes rcu_read_lock().
Note: there is no "Fixes" tag because this bug was there in a very
early stage.
Signed-off-by: Wei Wang <weiwan@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index ff38959..ed832b3 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -148,11 +148,23 @@
return fn;
}
-static void node_free(struct fib6_node *fn)
+static void node_free_immediate(struct fib6_node *fn)
{
kmem_cache_free(fib6_node_kmem, fn);
}
+static void node_free_rcu(struct rcu_head *head)
+{
+ struct fib6_node *fn = container_of(head, struct fib6_node, rcu);
+
+ kmem_cache_free(fib6_node_kmem, fn);
+}
+
+static void node_free(struct fib6_node *fn)
+{
+ call_rcu(&fn->rcu, node_free_rcu);
+}
+
static void rt6_rcu_free(struct rt6_info *rt)
{
call_rcu(&rt->dst.rcu_head, dst_rcu_free);
@@ -589,9 +601,9 @@
if (!in || !ln) {
if (in)
- node_free(in);
+ node_free_immediate(in);
if (ln)
- node_free(ln);
+ node_free_immediate(ln);
return ERR_PTR(-ENOMEM);
}
@@ -1020,7 +1032,7 @@
root, and then (in failure) stale node
in main tree.
*/
- node_free(sfn);
+ node_free_immediate(sfn);
err = PTR_ERR(sn);
goto failure;
}
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 5764a84..632987f 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1267,7 +1267,9 @@
static struct dst_entry *rt6_check(struct rt6_info *rt, u32 cookie)
{
- if (!rt->rt6i_node || (rt->rt6i_node->fn_sernum != cookie))
+ u32 rt_cookie;
+
+ if (!rt6_get_cookie_safe(rt, &rt_cookie) || rt_cookie != cookie)
return NULL;
if (rt6_check_expired(rt))
@@ -1335,8 +1337,14 @@
if (rt->rt6i_flags & RTF_CACHE) {
dst_hold(&rt->dst);
ip6_del_rt(rt);
- } else if (rt->rt6i_node && (rt->rt6i_flags & RTF_DEFAULT)) {
- rt->rt6i_node->fn_sernum = -1;
+ } else {
+ struct fib6_node *fn;
+
+ rcu_read_lock();
+ fn = rcu_dereference(rt->rt6i_node);
+ if (fn && (rt->rt6i_flags & RTF_DEFAULT))
+ fn->fn_sernum = -1;
+ rcu_read_unlock();
}
}
}