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drivers, net: convert masces_rx_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_rx_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>
This commit is contained in:
Elena Reshetova 2017-10-20 10:23:43 +03:00 committed by David S. Miller
parent 956cc1e70c
commit e187246f0f
1 changed files with 5 additions and 4 deletions
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9
drivers/net/macsec.c
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@ -16,6 +16,7 @@
#include <crypto/aead.h>
#include <linux/etherdevice.h>
#include <linux/rtnetlink.h>
#include <linux/refcount.h>
#include <net/genetlink.h>
#include <net/sock.h>
#include <net/gro_cells.h>
@ -146,7 +147,7 @@ struct macsec_rx_sa {
struct macsec_key key;
spinlock_t lock;
u32 next_pn;
atomic_t refcnt;
refcount_t refcnt;
bool active;
struct macsec_rx_sa_stats __percpu *stats;
struct macsec_rx_sc *sc;
@ -314,7 +315,7 @@ static struct macsec_rx_sa *macsec_rxsa_get(struct macsec_rx_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;
@ -350,7 +351,7 @@ static void free_rxsa(struct rcu_head *head)
static void macsec_rxsa_put(struct macsec_rx_sa *sa)
{
if (atomic_dec_and_test(&sa->refcnt))
if (refcount_dec_and_test(&sa->refcnt))
call_rcu(&sa->rcu, free_rxsa);
}
@ -1339,7 +1340,7 @@ static int init_rx_sa(struct macsec_rx_sa *rx_sa, char *sak, int key_len,
rx_sa->active = false;
rx_sa->next_pn = 1;
atomic_set(&rx_sa->refcnt, 1);
refcount_set(&rx_sa->refcnt, 1);
spin_lock_init(&rx_sa->lock);
return 0;