net/ipv6: Revert remove expired routes with a separated list of routes

This reverts commit 3dec89b.

The commit has some race conditions given how expires is managed on a
fib6_info in relation to gc start, adding the entry to the gc list and
setting the timer value leading to UAF. Revert the commit and try again
in a later release.

Fixes: 3dec89b ("net/ipv6: Remove expired routes with a separated list of routes")
Cc: Kui-Feng Lee <thinker.li@gmail.com>
Signed-off-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20231219030243.25687-1-dsahern@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: dsahern

include/net/ip6_fib.h

@@ -179,9 +179,6 @@ struct fib6_info {
 
 	refcount_t			fib6_ref;
 	unsigned long			expires;
-
-	struct hlist_node		gc_link;
-
 	struct dst_metrics		*fib6_metrics;
 #define fib6_pmtu		fib6_metrics->metrics[RTAX_MTU-1]
 
@@ -250,18 +247,26 @@ static inline bool fib6_requires_src(const struct fib6_info *rt)
 	return rt->fib6_src.plen > 0;
 }
 
+static inline void fib6_clean_expires(struct fib6_info *f6i)
+{
+	f6i->fib6_flags &= ~RTF_EXPIRES;
+	f6i->expires = 0;
+}
+
+static inline void fib6_set_expires(struct fib6_info *f6i,
+				    unsigned long expires)
+{
+	f6i->expires = expires;
+	f6i->fib6_flags |= RTF_EXPIRES;
+}
+
 static inline bool fib6_check_expired(const struct fib6_info *f6i)
 {
 	if (f6i->fib6_flags & RTF_EXPIRES)
 		return time_after(jiffies, f6i->expires);
 	return false;
 }
 
-static inline bool fib6_has_expires(const struct fib6_info *f6i)
-{
-	return f6i->fib6_flags & RTF_EXPIRES;
-}
-
 /* Function to safely get fn->fn_sernum for passed in rt
  * and store result in passed in cookie.
  * Return true if we can get cookie safely
@@ -383,7 +388,6 @@ struct fib6_table {
 	struct inet_peer_base	tb6_peers;
 	unsigned int		flags;
 	unsigned int		fib_seq;
-	struct hlist_head       tb6_gc_hlist;	/* GC candidates */
 #define RT6_TABLE_HAS_DFLT_ROUTER	BIT(0)
 };
 
@@ -500,48 +504,6 @@ void fib6_gc_cleanup(void);
 
 int fib6_init(void);
 
-/* fib6_info must be locked by the caller, and fib6_info->fib6_table can be
- * NULL.
- */
-static inline void fib6_set_expires_locked(struct fib6_info *f6i,
-					   unsigned long expires)
-{
-	struct fib6_table *tb6;
-
-	tb6 = f6i->fib6_table;
-	f6i->expires = expires;
-	if (tb6 && !fib6_has_expires(f6i))
-		hlist_add_head(&f6i->gc_link, &tb6->tb6_gc_hlist);
-	f6i->fib6_flags |= RTF_EXPIRES;
-}
-
-/* fib6_info must be locked by the caller, and fib6_info->fib6_table can be
- * NULL.  If fib6_table is NULL, the fib6_info will no be inserted into the
- * list of GC candidates until it is inserted into a table.
- */
-static inline void fib6_set_expires(struct fib6_info *f6i,
-				    unsigned long expires)
-{
-	spin_lock_bh(&f6i->fib6_table->tb6_lock);
-	fib6_set_expires_locked(f6i, expires);
-	spin_unlock_bh(&f6i->fib6_table->tb6_lock);
-}
-
-static inline void fib6_clean_expires_locked(struct fib6_info *f6i)
-{
-	if (fib6_has_expires(f6i))
-		hlist_del_init(&f6i->gc_link);
-	f6i->fib6_flags &= ~RTF_EXPIRES;
-	f6i->expires = 0;
-}
-
-static inline void fib6_clean_expires(struct fib6_info *f6i)
-{
-	spin_lock_bh(&f6i->fib6_table->tb6_lock);
-	fib6_clean_expires_locked(f6i);
-	spin_unlock_bh(&f6i->fib6_table->tb6_lock);
-}
-
 struct ipv6_route_iter {
 	struct seq_net_private p;
 	struct fib6_walker w;

net/ipv6/ip6_fib.c

@@ -160,8 +160,6 @@ struct fib6_info *fib6_info_alloc(gfp_t gfp_flags, bool with_fib6_nh)
 	INIT_LIST_HEAD(&f6i->fib6_siblings);
 	refcount_set(&f6i->fib6_ref, 1);
 
-	INIT_HLIST_NODE(&f6i->gc_link);
-
 	return f6i;
 }
 
@@ -248,7 +246,6 @@ static struct fib6_table *fib6_alloc_table(struct net *net, u32 id)
 				   net->ipv6.fib6_null_entry);
 		table->tb6_root.fn_flags = RTN_ROOT | RTN_TL_ROOT | RTN_RTINFO;
 		inet_peer_base_init(&table->tb6_peers);
-		INIT_HLIST_HEAD(&table->tb6_gc_hlist);
 	}
 
 	return table;
@@ -1060,8 +1057,6 @@ static void fib6_purge_rt(struct fib6_info *rt, struct fib6_node *fn,
 				    lockdep_is_held(&table->tb6_lock));
 		}
 	}
-
-	fib6_clean_expires_locked(rt);
 }
 
 /*
@@ -1123,10 +1118,9 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt,
 				if (!(iter->fib6_flags & RTF_EXPIRES))
 					return -EEXIST;
 				if (!(rt->fib6_flags & RTF_EXPIRES))
-					fib6_clean_expires_locked(iter);
+					fib6_clean_expires(iter);
 				else
-					fib6_set_expires_locked(iter,
-								rt->expires);
+					fib6_set_expires(iter, rt->expires);
 
 				if (rt->fib6_pmtu)
 					fib6_metric_set(iter, RTAX_MTU,
@@ -1485,10 +1479,6 @@ int fib6_add(struct fib6_node *root, struct fib6_info *rt,
 		if (rt->nh)
 			list_add(&rt->nh_list, &rt->nh->f6i_list);
 		__fib6_update_sernum_upto_root(rt, fib6_new_sernum(info->nl_net));
-
-		if (fib6_has_expires(rt))
-			hlist_add_head(&rt->gc_link, &table->tb6_gc_hlist);
-
 		fib6_start_gc(info->nl_net, rt);
 	}
 
@@ -2291,16 +2281,17 @@ static void fib6_flush_trees(struct net *net)
  *	Garbage collection
  */
 
-static int fib6_age(struct fib6_info *rt, struct fib6_gc_args *gc_args)
+static int fib6_age(struct fib6_info *rt, void *arg)
 {
+	struct fib6_gc_args *gc_args = arg;
 	unsigned long now = jiffies;
 
 	/*
 	 *	check addrconf expiration here.
 	 *	Routes are expired even if they are in use.
 	 */
 
-	if (fib6_has_expires(rt) && rt->expires) {
+	if (rt->fib6_flags & RTF_EXPIRES && rt->expires) {
 		if (time_after(now, rt->expires)) {
 			RT6_TRACE("expiring %p\n", rt);
 			return -1;
@@ -2317,40 +2308,6 @@ static int fib6_age(struct fib6_info *rt, struct fib6_gc_args *gc_args)
 	return 0;
 }
 
-static void fib6_gc_table(struct net *net,
-			  struct fib6_table *tb6,
-			  struct fib6_gc_args *gc_args)
-{
-	struct fib6_info *rt;
-	struct hlist_node *n;
-	struct nl_info info = {
-		.nl_net = net,
-		.skip_notify = false,
-	};
-
-	hlist_for_each_entry_safe(rt, n, &tb6->tb6_gc_hlist, gc_link)
-		if (fib6_age(rt, gc_args) == -1)
-			fib6_del(rt, &info);
-}
-
-static void fib6_gc_all(struct net *net, struct fib6_gc_args *gc_args)
-{
-	struct fib6_table *table;
-	struct hlist_head *head;
-	unsigned int h;
-
-	rcu_read_lock();
-	for (h = 0; h < FIB6_TABLE_HASHSZ; h++) {
-		head = &net->ipv6.fib_table_hash[h];
-		hlist_for_each_entry_rcu(table, head, tb6_hlist) {
-			spin_lock_bh(&table->tb6_lock);
-			fib6_gc_table(net, table, gc_args);
-			spin_unlock_bh(&table->tb6_lock);
-		}
-	}
-	rcu_read_unlock();
-}
-
 void fib6_run_gc(unsigned long expires, struct net *net, bool force)
 {
 	struct fib6_gc_args gc_args;
@@ -2366,7 +2323,7 @@ void fib6_run_gc(unsigned long expires, struct net *net, bool force)
 			  net->ipv6.sysctl.ip6_rt_gc_interval;
 	gc_args.more = 0;
 
-	fib6_gc_all(net, &gc_args);
+	fib6_clean_all(net, fib6_age, &gc_args);
 	now = jiffies;
 	net->ipv6.ip6_rt_last_gc = now;
 

net/ipv6/route.c

@@ -3763,10 +3763,10 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
 		rt->dst_nocount = true;
 
 	if (cfg->fc_flags & RTF_EXPIRES)
-		fib6_set_expires_locked(rt, jiffies +
-					clock_t_to_jiffies(cfg->fc_expires));
+		fib6_set_expires(rt, jiffies +
+				clock_t_to_jiffies(cfg->fc_expires));
 	else
-		fib6_clean_expires_locked(rt);
+		fib6_clean_expires(rt);
 
 	if (cfg->fc_protocol == RTPROT_UNSPEC)
 		cfg->fc_protocol = RTPROT_BOOT;