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]> --- net/netfilter/nfnetlink_acct.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/net/netfilter/nfnetlink_acct.c b/net/netfilter/nfnetlink_acct.c index d44d89b..f44cbd3 100644 --- a/net/netfilter/nfnetlink_acct.c +++ b/net/netfilter/nfnetlink_acct.c @@ -11,6 +11,7 @@ #include <linux/kernel.h> #include <linux/skbuff.h> #include <linux/atomic.h> +#include <linux/refcount.h> #include <linux/netlink.h> #include <linux/rculist.h> #include <linux/slab.h> @@ -32,7 +33,7 @@ struct nf_acct { atomic64_t bytes; unsigned long flags; struct list_head head; - atomic_t refcnt; + refcount_t refcnt; char name[NFACCT_NAME_MAX]; struct rcu_head rcu_head; char data[0]; @@ -123,7 +124,7 @@ static int nfnl_acct_new(struct net *net, struct sock *nfnl, atomic64_set(&nfacct->pkts, be64_to_cpu(nla_get_be64(tb[NFACCT_PKTS]))); } - atomic_set(&nfacct->refcnt, 1); + refcount_set(&nfacct->refcnt, 1); list_add_tail_rcu(&nfacct->head, &net->nfnl_acct_list); return 0; } @@ -166,7 +167,7 @@ nfnl_acct_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type, NFACCT_PAD) || nla_put_be64(skb, NFACCT_BYTES, cpu_to_be64(bytes), NFACCT_PAD) || - nla_put_be32(skb, NFACCT_USE, htonl(atomic_read(&acct->refcnt)))) + nla_put_be32(skb, NFACCT_USE, htonl(refcount_read(&acct->refcnt)))) goto nla_put_failure; if (acct->flags & NFACCT_F_QUOTA) { u64 *quota = (u64 *)acct->data; @@ -325,11 +326,12 @@ static int nfnl_acct_get(struct net *net, struct sock *nfnl, static int nfnl_acct_try_del(struct nf_acct *cur) { int ret = 0; + unsigned int refcount; /* We want to avoid races with nfnl_acct_put. So only when the current * refcnt is 1, we decrease it to 0. */ - if (atomic_cmpxchg(&cur->refcnt, 1, 0) == 1) { + if (refcount_dec_if_one(&cur->refcnt)) { /* We are protected by nfnl mutex. */ list_del_rcu(&cur->head); kfree_rcu(cur, rcu_head); @@ -413,7 +415,7 @@ struct nf_acct *nfnl_acct_find_get(struct net *net, const char *acct_name) if (!try_module_get(THIS_MODULE)) goto err; - if (!atomic_inc_not_zero(&cur->refcnt)) { + if (!refcount_inc_not_zero(&cur->refcnt)) { module_put(THIS_MODULE); goto err; } @@ -429,7 +431,7 @@ EXPORT_SYMBOL_GPL(nfnl_acct_find_get); void nfnl_acct_put(struct nf_acct *acct) { - if (atomic_dec_and_test(&acct->refcnt)) + if (refcount_dec_and_test(&acct->refcnt)) kfree_rcu(acct, rcu_head); module_put(THIS_MODULE); @@ -502,7 +504,7 @@ static void __net_exit nfnl_acct_net_exit(struct net *net) list_for_each_entry_safe(cur, tmp, &net->nfnl_acct_list, head) { list_del_rcu(&cur->head); - if (atomic_dec_and_test(&cur->refcnt)) + if (refcount_dec_and_test(&cur->refcnt)) kfree_rcu(cur, rcu_head); } } -- 2.7.4
