refcount_t type and corresponding API should be used instead of atomic_t when the variable is used as a reference counter. This allows to avoid accidental refcounter overflows that might lead to use-after-free situations.
Signed-off-by: Elena Reshetova <[email protected]> Signed-off-by: Hans Liljestrand <[email protected]> Signed-off-by: Kees Cook <[email protected]> Signed-off-by: David Windsor <[email protected]> --- include/net/netfilter/nf_conntrack_timeout.h | 3 ++- net/netfilter/nfnetlink_cttimeout.c | 12 ++++++------ 2 files changed, 8 insertions(+), 7 deletions(-) diff --git a/include/net/netfilter/nf_conntrack_timeout.h b/include/net/netfilter/nf_conntrack_timeout.h index 5cc5e9e..d40b893 100644 --- a/include/net/netfilter/nf_conntrack_timeout.h +++ b/include/net/netfilter/nf_conntrack_timeout.h @@ -4,6 +4,7 @@ #include <net/net_namespace.h> #include <linux/netfilter/nf_conntrack_common.h> #include <linux/netfilter/nf_conntrack_tuple_common.h> +#include <linux/refcount.h> #include <net/netfilter/nf_conntrack.h> #include <net/netfilter/nf_conntrack_extend.h> @@ -12,7 +13,7 @@ struct ctnl_timeout { struct list_head head; struct rcu_head rcu_head; - atomic_t refcnt; + refcount_t refcnt; char name[CTNL_TIMEOUT_NAME_MAX]; __u16 l3num; struct nf_conntrack_l4proto *l4proto; diff --git a/net/netfilter/nfnetlink_cttimeout.c b/net/netfilter/nfnetlink_cttimeout.c index 139e086..baa75f3 100644 --- a/net/netfilter/nfnetlink_cttimeout.c +++ b/net/netfilter/nfnetlink_cttimeout.c @@ -138,7 +138,7 @@ static int cttimeout_new_timeout(struct net *net, struct sock *ctnl, strcpy(timeout->name, nla_data(cda[CTA_TIMEOUT_NAME])); timeout->l3num = l3num; timeout->l4proto = l4proto; - atomic_set(&timeout->refcnt, 1); + refcount_set(&timeout->refcnt, 1); list_add_tail_rcu(&timeout->head, &net->nfct_timeout_list); return 0; @@ -172,7 +172,7 @@ ctnl_timeout_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type, nla_put_be16(skb, CTA_TIMEOUT_L3PROTO, htons(timeout->l3num)) || nla_put_u8(skb, CTA_TIMEOUT_L4PROTO, timeout->l4proto->l4proto) || nla_put_be32(skb, CTA_TIMEOUT_USE, - htonl(atomic_read(&timeout->refcnt)))) + htonl(refcount_read(&timeout->refcnt)))) goto nla_put_failure; if (likely(l4proto->ctnl_timeout.obj_to_nlattr)) { @@ -339,7 +339,7 @@ static int ctnl_timeout_try_del(struct net *net, struct ctnl_timeout *timeout) /* We want to avoid races with ctnl_timeout_put. So only when the * current refcnt is 1, we decrease it to 0. */ - if (atomic_cmpxchg(&timeout->refcnt, 1, 0) == 1) { + if (refcount_dec_if_one(&timeout->refcnt)) { /* We are protected by nfnl mutex. */ list_del_rcu(&timeout->head); nf_ct_l4proto_put(timeout->l4proto); @@ -536,7 +536,7 @@ ctnl_timeout_find_get(struct net *net, const char *name) if (!try_module_get(THIS_MODULE)) goto err; - if (!atomic_inc_not_zero(&timeout->refcnt)) { + if (!refcount_inc_not_zero(&timeout->refcnt)) { module_put(THIS_MODULE); goto err; } @@ -550,7 +550,7 @@ ctnl_timeout_find_get(struct net *net, const char *name) static void ctnl_timeout_put(struct ctnl_timeout *timeout) { - if (atomic_dec_and_test(&timeout->refcnt)) + if (refcount_dec_and_test(&timeout->refcnt)) kfree_rcu(timeout, rcu_head); module_put(THIS_MODULE); @@ -601,7 +601,7 @@ static void __net_exit cttimeout_net_exit(struct net *net) list_del_rcu(&cur->head); nf_ct_l4proto_put(cur->l4proto); - if (atomic_dec_and_test(&cur->refcnt)) + if (refcount_dec_and_test(&cur->refcnt)) kfree_rcu(cur, rcu_head); } } -- 2.7.4
