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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 <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>
hifive-unleashed-5.1
Elena Reshetova 2017-10-20 10:23:45 +03:00 committed by David S. Miller
parent 8676d76f08
commit 28206cdb3b
1 changed files with 4 additions and 4 deletions
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8
drivers/net/macsec.c
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@ -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;