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authorWei Wang <weiwan@google.com>2017-08-21 09:47:10 -0700
committerDavid S. Miller <davem@davemloft.net>2017-08-22 11:03:19 -0700
commitc5cff8561d2d0006e972bd114afd51f082fee77c (patch)
tree590d33658f2a4a6add9db5734988b80a5313efc8 /include/net/ip6_fib.h
parent0c8d2d95b815c7610720b7e868b395a019864720 (diff)
ipv6: add rcu grace period before freeing fib6_node
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>
Diffstat (limited to 'include/net/ip6_fib.h')
-rw-r--r--include/net/ip6_fib.h30
1 files changed, 29 insertions, 1 deletions
diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 1a88008cc6f5..e9c59db92942 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -70,6 +70,7 @@ struct fib6_node {
__u16 fn_flags;
int fn_sernum;
struct rt6_info *rr_ptr;
+ struct rcu_head rcu;
};
#ifndef CONFIG_IPV6_SUBTREES
@@ -167,13 +168,40 @@ static inline void rt6_update_expires(struct rt6_info *rt0, int timeout)
rt0->rt6i_flags |= RTF_EXPIRES;
}
+/* Function to safely get fn->sernum for passed in rt
+ * and store result in passed in cookie.
+ * Return true if we can get cookie safely
+ * Return false if not
+ */
+static inline bool rt6_get_cookie_safe(const struct rt6_info *rt,
+ u32 *cookie)
+{
+ struct fib6_node *fn;
+ bool status = false;
+
+ rcu_read_lock();
+ fn = rcu_dereference(rt->rt6i_node);
+
+ if (fn) {
+ *cookie = fn->fn_sernum;
+ status = true;
+ }
+
+ rcu_read_unlock();
+ return status;
+}
+
static inline u32 rt6_get_cookie(const struct rt6_info *rt)
{
+ u32 cookie = 0;
+
if (rt->rt6i_flags & RTF_PCPU ||
(unlikely(!list_empty(&rt->rt6i_uncached)) && rt->dst.from))
rt = (struct rt6_info *)(rt->dst.from);
- return rt->rt6i_node ? rt->rt6i_node->fn_sernum : 0;
+ rt6_get_cookie_safe(rt, &cookie);
+
+ return cookie;
}
static inline void ip6_rt_put(struct rt6_info *rt)