From: Elena Reshetova Date: Fri, 20 Oct 2017 07:23:45 +0000 (+0300) Subject: drivers, net: convert masces_tx_sa.refcnt from atomic_t to refcount_t X-Git-Tag: v4.15-rc1~84^2~367^2~4 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=28206cdb3bc079a97d24c33b4427395f9e406fad;p=linux.git drivers, net: convert masces_tx_sa.refcnt from atomic_t to refcount_t atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable masces_tx_sa.refcnt is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova Signed-off-by: David S. Miller --- diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c index e0aeb51a5dab..8948b6adc0c5 100644 --- a/drivers/net/macsec.c +++ b/drivers/net/macsec.c @@ -188,7 +188,7 @@ struct macsec_tx_sa { struct macsec_key key; spinlock_t lock; u32 next_pn; - atomic_t refcnt; + refcount_t refcnt; bool active; struct macsec_tx_sa_stats __percpu *stats; struct rcu_head rcu; @@ -362,7 +362,7 @@ static struct macsec_tx_sa *macsec_txsa_get(struct macsec_tx_sa __rcu *ptr) if (!sa || !sa->active) return NULL; - if (!atomic_inc_not_zero(&sa->refcnt)) + if (!refcount_inc_not_zero(&sa->refcnt)) return NULL; return sa; @@ -379,7 +379,7 @@ static void free_txsa(struct rcu_head *head) static void macsec_txsa_put(struct macsec_tx_sa *sa) { - if (atomic_dec_and_test(&sa->refcnt)) + if (refcount_dec_and_test(&sa->refcnt)) call_rcu(&sa->rcu, free_txsa); } @@ -1437,7 +1437,7 @@ static int init_tx_sa(struct macsec_tx_sa *tx_sa, char *sak, int key_len, } tx_sa->active = false; - atomic_set(&tx_sa->refcnt, 1); + refcount_set(&tx_sa->refcnt, 1); spin_lock_init(&tx_sa->lock); return 0;