Merge branch 'ipv6-Another-followup-to-the-fib6_info-change'

David Ahern says:

====================
net/ipv6: Another followup to the fib6_info change

Last one - for this week.

Patches 1, 2 and 7 are more cleanup patches - removing dead code,
moving code from a header to near its single caller, and updating
function name.

Patches 3-5 do some refactoring leading up to patch 6 which fixes
a NULL dereference. I have only managed to trigger a panic once, so
I can not definitively confirm it addresses the problem but it seems
pretty clear that it is a race on removing a 'from' reference on
an rt6_info and another path using that 'from' value to do
cookie checking.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 29 deletions

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 642211174692..1af450d4e923 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -174,7 +174,7 @@ struct fib6_info {
 
 struct rt6_info {
 	struct dst_entry		dst;
-	struct fib6_info		*from;
+	struct fib6_info __rcu		*from;
 
 	struct rt6key			rt6i_dst;
 	struct rt6key			rt6i_src;
@@ -223,39 +223,17 @@ static inline bool fib6_check_expired(const struct fib6_info *f6i)
 	return false;
 }
 
-static inline void rt6_clean_expires(struct rt6_info *rt)
-{
-	rt->rt6i_flags &= ~RTF_EXPIRES;
-	rt->dst.expires = 0;
-}
-
-static inline void rt6_set_expires(struct rt6_info *rt, unsigned long expires)
-{
-	rt->dst.expires = expires;
-	rt->rt6i_flags |= RTF_EXPIRES;
-}
-
-static inline void rt6_update_expires(struct rt6_info *rt0, int timeout)
-{
-	if (!(rt0->rt6i_flags & RTF_EXPIRES) && rt0->from)
-		rt0->dst.expires = rt0->from->expires;
-
-	dst_set_expires(&rt0->dst, 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 fib6_info *f6i,
-				       u32 *cookie)
+static inline bool fib6_get_cookie_safe(const struct fib6_info *f6i,
+					u32 *cookie)
 {
 	struct fib6_node *fn;
 	bool status = false;
 
-	rcu_read_lock();
 	fn = rcu_dereference(f6i->fib6_node);
 
 	if (fn) {
@@ -265,17 +243,22 @@ static inline bool rt6_get_cookie_safe(const struct fib6_info *f6i,
 		status = true;
 	}
 
-	rcu_read_unlock();
 	return status;
 }
 
 static inline u32 rt6_get_cookie(const struct rt6_info *rt)
 {
+	struct fib6_info *from;
 	u32 cookie = 0;
 
-	if (rt->rt6i_flags & RTF_PCPU ||
-	    (unlikely(!list_empty(&rt->rt6i_uncached)) && rt->from))
-		rt6_get_cookie_safe(rt->from, &cookie);
+	rcu_read_lock();
+
+	from = rcu_dereference(rt->from);
+	if (from && (rt->rt6i_flags & RTF_PCPU ||
+	    unlikely(!list_empty(&rt->rt6i_uncached))))
+		fib6_get_cookie_safe(from, &cookie);
+
+	rcu_read_unlock();
 
 	return cookie;
 }