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 <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 e0aeb51..8948b6a 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;
--
2.7.4
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