From 8e3d5be7368107f0c27a1f8126d79b01a47e9567 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Tue, 15 Sep 2015 14:30:08 -0700 Subject: [PATCH] ipv6: Avoid double dst_free It is a prep work to get dst freeing from fib tree undergo a rcu grace period. The following is a common paradigm: if (ip6_del_rt(rt)) dst_free(rt) which means, if rt cannot be deleted from the fib tree, dst_free(rt) now. 1. We don't know the ip6_del_rt(rt) failure is because it was not managed by fib tree (e.g. DST_NOCACHE) or it had already been removed from the fib tree. 2. If rt had been managed by the fib tree, ip6_del_rt(rt) failure means dst_free(rt) has been called already. A second dst_free(rt) is not always obviously safe. The rt may have been destroyed already. 3. If rt is a DST_NOCACHE, dst_free(rt) should not be called. 4. It is a stopper to make dst freeing from fib tree undergo a rcu grace period. This patch is to use a DST_NOCACHE flag to indicate a rt is not managed by the fib tree. Signed-off-by: Martin KaFai Lau Signed-off-by: David S. Miller --- net/ipv6/addrconf.c | 7 +++---- net/ipv6/ip6_fib.c | 11 +++++++++-- net/ipv6/route.c | 7 ++++--- 3 files changed, 16 insertions(+), 9 deletions(-) diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 030fefdc9aed..900113376d4e 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -5127,13 +5127,12 @@ static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp) rt = addrconf_get_prefix_route(&ifp->peer_addr, 128, ifp->idev->dev, 0, 0); - if (rt && ip6_del_rt(rt)) - dst_free(&rt->dst); + if (rt) + ip6_del_rt(rt); } dst_hold(&ifp->rt->dst); - if (ip6_del_rt(ifp->rt)) - dst_free(&ifp->rt->dst); + ip6_del_rt(ifp->rt); rt_genid_bump_ipv6(net); break; diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index 418d9823692b..e68350bf838b 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -933,6 +933,10 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, int replace_required = 0; int sernum = fib6_new_sernum(info->nl_net); + if (WARN_ON_ONCE((rt->dst.flags & DST_NOCACHE) && + !atomic_read(&rt->dst.__refcnt))) + return -EINVAL; + if (info->nlh) { if (!(info->nlh->nlmsg_flags & NLM_F_CREATE)) allow_create = 0; @@ -1025,6 +1029,7 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, fib6_start_gc(info->nl_net, rt); if (!(rt->rt6i_flags & RTF_CACHE)) fib6_prune_clones(info->nl_net, pn); + rt->dst.flags &= ~DST_NOCACHE; } out: @@ -1049,7 +1054,8 @@ out: atomic_inc(&pn->leaf->rt6i_ref); } #endif - dst_free(&rt->dst); + if (!(rt->dst.flags & DST_NOCACHE)) + dst_free(&rt->dst); } return err; @@ -1060,7 +1066,8 @@ out: st_failure: if (fn && !(fn->fn_flags & (RTN_RTINFO|RTN_ROOT))) fib6_repair_tree(info->nl_net, fn); - dst_free(&rt->dst); + if (!(rt->dst.flags & DST_NOCACHE)) + dst_free(&rt->dst); return err; #endif } diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 53617d715188..3d3c1b294725 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -1322,8 +1322,7 @@ static void ip6_link_failure(struct sk_buff *skb) if (rt) { if (rt->rt6i_flags & RTF_CACHE) { dst_hold(&rt->dst); - if (ip6_del_rt(rt)) - dst_free(&rt->dst); + ip6_del_rt(rt); } else if (rt->rt6i_node && (rt->rt6i_flags & RTF_DEFAULT)) { rt->rt6i_node->fn_sernum = -1; } @@ -2028,7 +2027,8 @@ static int __ip6_del_rt(struct rt6_info *rt, struct nl_info *info) struct fib6_table *table; struct net *net = dev_net(rt->dst.dev); - if (rt == net->ipv6.ip6_null_entry) { + if (rt == net->ipv6.ip6_null_entry || + rt->dst.flags & DST_NOCACHE) { err = -ENOENT; goto out; } @@ -2515,6 +2515,7 @@ struct rt6_info *addrconf_dst_alloc(struct inet6_dev *idev, rt->rt6i_dst.addr = *addr; rt->rt6i_dst.plen = 128; rt->rt6i_table = fib6_get_table(net, RT6_TABLE_LOCAL); + rt->dst.flags |= DST_NOCACHE; atomic_set(&rt->dst.__refcnt, 1); -- 2.20.1