[PATCH 1/9] netfilter: ipset: fix race condition in ipset save, swap and delete
From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: 2016-03-28 17:58:11
Also in:
netfilter-devel
Subsystem:
netfilter, networking [general], the rest · Maintainers:
Pablo Neira Ayuso, Florian Westphal, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Vishwanath Pai <redacted> This fix adds a new reference counter (ref_netlink) for the struct ip_set. The other reference counter (ref) can be swapped out by ip_set_swap and we need a separate counter to keep track of references for netlink events like dump. Using the same ref counter for dump causes a race condition which can be demonstrated by the following script: ipset create hash_ip1 hash:ip family inet hashsize 1024 maxelem 500000 \ counters ipset create hash_ip2 hash:ip family inet hashsize 300000 maxelem 500000 \ counters ipset create hash_ip3 hash:ip family inet hashsize 1024 maxelem 500000 \ counters ipset save & ipset swap hash_ip3 hash_ip2 ipset destroy hash_ip3 /* will crash the machine */ Swap will exchange the values of ref so destroy will see ref = 0 instead of ref = 1. With this fix in place swap will not succeed because ipset save still has ref_netlink on the set (ip_set_swap doesn't swap ref_netlink). Both delete and swap will error out if ref_netlink != 0 on the set. Note: The changes to *_head functions is because previously we would increment ref whenever we called these functions, we don't do that anymore. Reviewed-by: Joshua Hunt <redacted> Signed-off-by: Vishwanath Pai <redacted> Signed-off-by: Jozsef Kadlecsik <redacted> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> --- include/linux/netfilter/ipset/ip_set.h | 4 ++++ net/netfilter/ipset/ip_set_bitmap_gen.h | 2 +- net/netfilter/ipset/ip_set_core.c | 33 ++++++++++++++++++++++++++++----- net/netfilter/ipset/ip_set_hash_gen.h | 2 +- net/netfilter/ipset/ip_set_list_set.c | 2 +- 5 files changed, 35 insertions(+), 8 deletions(-)
diff --git a/include/linux/netfilter/ipset/ip_set.h b/include/linux/netfilter/ipset/ip_set.h
index 0e1f433..f48b8a6 100644
--- a/include/linux/netfilter/ipset/ip_set.h
+++ b/include/linux/netfilter/ipset/ip_set.h@@ -234,6 +234,10 @@ struct ip_set { spinlock_t lock; /* References to the set */ u32 ref; + /* References to the set for netlink events like dump, + * ref can be swapped out by ip_set_swap + */ + u32 ref_netlink; /* The core set type */ struct ip_set_type *type; /* The type variant doing the real job */
diff --git a/net/netfilter/ipset/ip_set_bitmap_gen.h b/net/netfilter/ipset/ip_set_bitmap_gen.h
index b0bc475..2e8e7e5 100644
--- a/net/netfilter/ipset/ip_set_bitmap_gen.h
+++ b/net/netfilter/ipset/ip_set_bitmap_gen.h@@ -95,7 +95,7 @@ mtype_head(struct ip_set *set, struct sk_buff *skb) if (!nested) goto nla_put_failure; if (mtype_do_head(skb, map) || - nla_put_net32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref - 1)) || + nla_put_net32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref)) || nla_put_net32(skb, IPSET_ATTR_MEMSIZE, htonl(memsize))) goto nla_put_failure; if (unlikely(ip_set_put_flags(skb, set)))
diff --git a/net/netfilter/ipset/ip_set_core.c b/net/netfilter/ipset/ip_set_core.c
index 7e6568c..a748b0c 100644
--- a/net/netfilter/ipset/ip_set_core.c
+++ b/net/netfilter/ipset/ip_set_core.c@@ -497,6 +497,26 @@ __ip_set_put(struct ip_set *set) write_unlock_bh(&ip_set_ref_lock); } +/* set->ref can be swapped out by ip_set_swap, netlink events (like dump) need + * a separate reference counter + */ +static inline void +__ip_set_get_netlink(struct ip_set *set) +{ + write_lock_bh(&ip_set_ref_lock); + set->ref_netlink++; + write_unlock_bh(&ip_set_ref_lock); +} + +static inline void +__ip_set_put_netlink(struct ip_set *set) +{ + write_lock_bh(&ip_set_ref_lock); + BUG_ON(set->ref_netlink == 0); + set->ref_netlink--; + write_unlock_bh(&ip_set_ref_lock); +} + /* Add, del and test set entries from kernel. * * The set behind the index must exist and must be referenced
@@ -1002,7 +1022,7 @@ static int ip_set_destroy(struct net *net, struct sock *ctnl, if (!attr[IPSET_ATTR_SETNAME]) { for (i = 0; i < inst->ip_set_max; i++) { s = ip_set(inst, i); - if (s && s->ref) { + if (s && (s->ref || s->ref_netlink)) { ret = -IPSET_ERR_BUSY; goto out; }
@@ -1024,7 +1044,7 @@ static int ip_set_destroy(struct net *net, struct sock *ctnl, if (!s) { ret = -ENOENT; goto out; - } else if (s->ref) { + } else if (s->ref || s->ref_netlink) { ret = -IPSET_ERR_BUSY; goto out; }
@@ -1171,6 +1191,9 @@ static int ip_set_swap(struct net *net, struct sock *ctnl, struct sk_buff *skb, from->family == to->family)) return -IPSET_ERR_TYPE_MISMATCH; + if (from->ref_netlink || to->ref_netlink) + return -EBUSY; + strncpy(from_name, from->name, IPSET_MAXNAMELEN); strncpy(from->name, to->name, IPSET_MAXNAMELEN); strncpy(to->name, from_name, IPSET_MAXNAMELEN);
@@ -1206,7 +1229,7 @@ ip_set_dump_done(struct netlink_callback *cb) if (set->variant->uref) set->variant->uref(set, cb, false); pr_debug("release set %s\n", set->name); - __ip_set_put_byindex(inst, index); + __ip_set_put_netlink(set); } return 0; }
@@ -1328,7 +1351,7 @@ dump_last: if (!cb->args[IPSET_CB_ARG0]) { /* Start listing: make sure set won't be destroyed */ pr_debug("reference set\n"); - set->ref++; + set->ref_netlink++; } write_unlock_bh(&ip_set_ref_lock); nlh = start_msg(skb, NETLINK_CB(cb->skb).portid,
@@ -1396,7 +1419,7 @@ release_refcount: if (set->variant->uref) set->variant->uref(set, cb, false); pr_debug("release set %s\n", set->name); - __ip_set_put_byindex(inst, index); + __ip_set_put_netlink(set); cb->args[IPSET_CB_ARG0] = 0; } out:
diff --git a/net/netfilter/ipset/ip_set_hash_gen.h b/net/netfilter/ipset/ip_set_hash_gen.h
index e5336ab..d32fd6b 100644
--- a/net/netfilter/ipset/ip_set_hash_gen.h
+++ b/net/netfilter/ipset/ip_set_hash_gen.h@@ -1082,7 +1082,7 @@ mtype_head(struct ip_set *set, struct sk_buff *skb) if (nla_put_u32(skb, IPSET_ATTR_MARKMASK, h->markmask)) goto nla_put_failure; #endif - if (nla_put_net32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref - 1)) || + if (nla_put_net32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref)) || nla_put_net32(skb, IPSET_ATTR_MEMSIZE, htonl(memsize))) goto nla_put_failure; if (unlikely(ip_set_put_flags(skb, set)))
diff --git a/net/netfilter/ipset/ip_set_list_set.c b/net/netfilter/ipset/ip_set_list_set.c
index 24c6c19..a2a89e4 100644
--- a/net/netfilter/ipset/ip_set_list_set.c
+++ b/net/netfilter/ipset/ip_set_list_set.c@@ -458,7 +458,7 @@ list_set_head(struct ip_set *set, struct sk_buff *skb) if (!nested) goto nla_put_failure; if (nla_put_net32(skb, IPSET_ATTR_SIZE, htonl(map->size)) || - nla_put_net32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref - 1)) || + nla_put_net32(skb, IPSET_ATTR_REFERENCES, htonl(set->ref)) || nla_put_net32(skb, IPSET_ATTR_MEMSIZE, htonl(sizeof(*map) + n * set->dsize))) goto nla_put_failure;
--
2.1.4