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drivers, net: convert masces_rx_sc.refcnt from atomic_t to refcount_t

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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@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Elena Reshetova 2017-10-20 10:23:44 +03:00 • committed by David S. Miller
parent e187246f0f
commit 8676d76f08
1 changed files with 4 additions and 4 deletions
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8
drivers/net/macsec.c
View file

@ -172,7 +172,7 @@ struct macsec_rx_sc {
bool active; bool active;
struct macsec_rx_sa __rcu *sa[MACSEC_NUM_AN]; struct macsec_rx_sa __rcu *sa[MACSEC_NUM_AN];
struct pcpu_rx_sc_stats __percpu *stats; struct pcpu_rx_sc_stats __percpu *stats;
atomic_t refcnt; refcount_t refcnt;
struct rcu_head rcu_head; 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) 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) 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); 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->sci = sci;
rx_sc->active = true; rx_sc->active = true;
atomic_set(&rx_sc->refcnt, 1); refcount_set(&rx_sc->refcnt, 1);
secy = &macsec_priv(dev)->secy; secy = &macsec_priv(dev)->secy;
rcu_assign_pointer(rx_sc->next, secy->rx_sc); rcu_assign_pointer(rx_sc->next, secy->rx_sc);