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_rx_sc.refcnt is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: David Windsor <dwindsor@xxxxxxxxx>
Reviewed-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
---
drivers/net/macsec.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index 733e1c2..e0aeb51 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -172,7 +172,7 @@ struct macsec_rx_sc {
bool active;
struct macsec_rx_sa __rcu *sa[MACSEC_NUM_AN];
struct pcpu_rx_sc_stats __percpu *stats;
- atomic_t refcnt;
+ refcount_t refcnt;
struct rcu_head rcu_head;
};
@@ -331,12 +331,12 @@ static void free_rx_sc_rcu(struct rcu_head *head)
static struct macsec_rx_sc *macsec_rxsc_get(struct macsec_rx_sc *sc)
{
- return atomic_inc_not_zero(&sc->refcnt) ? sc : NULL;
+ return refcount_inc_not_zero(&sc->refcnt) ? sc : NULL;
}
static void macsec_rxsc_put(struct macsec_rx_sc *sc)
{
- if (atomic_dec_and_test(&sc->refcnt))
+ if (refcount_dec_and_test(&sc->refcnt))
call_rcu(&sc->rcu_head, free_rx_sc_rcu);
}
@@ -1411,7 +1411,7 @@ static struct macsec_rx_sc *create_rx_sc(struct net_device *dev, sci_t sci)
rx_sc->sci = sci;
rx_sc->active = true;
- atomic_set(&rx_sc->refcnt, 1);
+ refcount_set(&rx_sc->refcnt, 1);
secy = &macsec_priv(dev)->secy;
rcu_assign_pointer(rx_sc->next, secy->rx_sc);
--
2.7.4
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