Merge branch 'ipv6-fib6_ref-conversion-to-refcount_t'

Eric Dumazet says:

====================
ipv6: fib6_ref conversion to refcount_t

We are chasing use-after-free in IPv6 that could have their origin
in fib6_ref 0 -> 1 transitions.

This patch series should help finding the root causes if these
illegal transitions ever happen.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip6_fib.h

@@ -146,7 +146,7 @@ struct fib6_info {
 	struct list_head		fib6_siblings;
 	unsigned int			fib6_nsiblings;
 
-	atomic_t			fib6_ref;
+	refcount_t			fib6_ref;
 	unsigned long			expires;
 	struct dst_metrics		*fib6_metrics;
 #define fib6_pmtu		fib6_metrics->metrics[RTAX_MTU-1]
@@ -284,17 +284,17 @@ void fib6_info_destroy_rcu(struct rcu_head *head);
 
 static inline void fib6_info_hold(struct fib6_info *f6i)
 {
-	atomic_inc(&f6i->fib6_ref);
+	refcount_inc(&f6i->fib6_ref);
 }
 
 static inline bool fib6_info_hold_safe(struct fib6_info *f6i)
 {
-	return atomic_inc_not_zero(&f6i->fib6_ref);
+	return refcount_inc_not_zero(&f6i->fib6_ref);
 }
 
 static inline void fib6_info_release(struct fib6_info *f6i)
 {
-	if (f6i && atomic_dec_and_test(&f6i->fib6_ref))
+	if (f6i && refcount_dec_and_test(&f6i->fib6_ref))
 		call_rcu(&f6i->rcu, fib6_info_destroy_rcu);
 }
 

net/ipv6/ip6_fib.c

@@ -162,7 +162,7 @@ struct fib6_info *fib6_info_alloc(gfp_t gfp_flags)
 	}
 
 	INIT_LIST_HEAD(&f6i->fib6_siblings);
-	atomic_inc(&f6i->fib6_ref);
+	refcount_set(&f6i->fib6_ref, 1);
 
 	return f6i;
 }
@@ -175,10 +175,7 @@ void fib6_info_destroy_rcu(struct rcu_head *head)
 	WARN_ON(f6i->fib6_node);
 
 	bucket = rcu_dereference_protected(f6i->rt6i_exception_bucket, 1);
-	if (bucket) {
-		f6i->rt6i_exception_bucket = NULL;
-		kfree(bucket);
-	}
+	kfree(bucket);
 
 	if (f6i->rt6i_pcpu) {
 		int cpu;
@@ -849,8 +846,8 @@ static struct fib6_node *fib6_add_1(struct net *net,
 
 		RCU_INIT_POINTER(in->parent, pn);
 		in->leaf = fn->leaf;
-		atomic_inc(&rcu_dereference_protected(in->leaf,
-				lockdep_is_held(&table->tb6_lock))->fib6_ref);
+		fib6_info_hold(rcu_dereference_protected(in->leaf,
+				lockdep_is_held(&table->tb6_lock)));
 
 		/* update parent pointer */
 		if (dir)
@@ -932,7 +929,7 @@ static void fib6_purge_rt(struct fib6_info *rt, struct fib6_node *fn,
 {
 	struct fib6_table *table = rt->fib6_table;
 
-	if (atomic_read(&rt->fib6_ref) != 1) {
+	if (refcount_read(&rt->fib6_ref) != 1) {
 		/* This route is used as dummy address holder in some split
 		 * nodes. It is not leaked, but it still holds other resources,
 		 * which must be released in time. So, scan ascendant nodes
@@ -945,7 +942,7 @@ static void fib6_purge_rt(struct fib6_info *rt, struct fib6_node *fn,
 			struct fib6_info *new_leaf;
 			if (!(fn->fn_flags & RTN_RTINFO) && leaf == rt) {
 				new_leaf = fib6_find_prefix(net, table, fn);
-				atomic_inc(&new_leaf->fib6_ref);
+				fib6_info_hold(new_leaf);
 
 				rcu_assign_pointer(fn->leaf, new_leaf);
 				fib6_info_release(rt);
@@ -1111,7 +1108,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt,
 			return err;
 
 		rcu_assign_pointer(rt->fib6_next, iter);
-		atomic_inc(&rt->fib6_ref);
+		fib6_info_hold(rt);
 		rcu_assign_pointer(rt->fib6_node, fn);
 		rcu_assign_pointer(*ins, rt);
 		if (!info->skip_notify)
@@ -1139,7 +1136,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt,
 		if (err)
 			return err;
 
-		atomic_inc(&rt->fib6_ref);
+		fib6_info_hold(rt);
 		rcu_assign_pointer(rt->fib6_node, fn);
 		rt->fib6_next = iter->fib6_next;
 		rcu_assign_pointer(*ins, rt);
@@ -1281,7 +1278,7 @@ int fib6_add(struct fib6_node *root, struct fib6_info *rt,
 			if (!sfn)
 				goto failure;
 
-			atomic_inc(&info->nl_net->ipv6.fib6_null_entry->fib6_ref);
+			fib6_info_hold(info->nl_net->ipv6.fib6_null_entry);
 			rcu_assign_pointer(sfn->leaf,
 					   info->nl_net->ipv6.fib6_null_entry);
 			sfn->fn_flags = RTN_ROOT;
@@ -1324,7 +1321,7 @@ int fib6_add(struct fib6_node *root, struct fib6_info *rt,
 				rcu_assign_pointer(fn->leaf,
 					    info->nl_net->ipv6.fib6_null_entry);
 			} else {
-				atomic_inc(&rt->fib6_ref);
+				fib6_info_hold(rt);
 				rcu_assign_pointer(fn->leaf, rt);
 			}
 		}
@@ -2314,7 +2311,7 @@ static int ipv6_route_seq_show(struct seq_file *seq, void *v)
 
 	dev = rt->fib6_nh.fib_nh_dev;
 	seq_printf(seq, " %08x %08x %08x %08x %8s\n",
-		   rt->fib6_metric, atomic_read(&rt->fib6_ref), 0,
+		   rt->fib6_metric, refcount_read(&rt->fib6_ref), 0,
 		   flags, dev ? dev->name : "");
 	iter->w.leaf = NULL;
 	return 0;

net/ipv6/route.c

@@ -296,7 +296,7 @@ static const struct fib6_info fib6_null_entry_template = {
 	.fib6_flags	= (RTF_REJECT | RTF_NONEXTHOP),
 	.fib6_protocol  = RTPROT_KERNEL,
 	.fib6_metric	= ~(u32)0,
-	.fib6_ref	= ATOMIC_INIT(1),
+	.fib6_ref	= REFCOUNT_INIT(1),
 	.fib6_type	= RTN_UNREACHABLE,
 	.fib6_metrics	= (struct dst_metrics *)&dst_default_metrics,
 };