drivers, net, mlx4: convert mlx4_qp.refcount 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 mlx4_qp.refcount 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>

diff --git a/drivers/net/ethernet/mellanox/mlx4/qp.c b/drivers/net/ethernet/mellanox/mlx4/qp.c
index 203320923340e4b52bb8fbe59334ebda18d234b2..769598f7b6c87eb83540c88678570869e6ca8d26 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/qp.c
+++ b/drivers/net/ethernet/mellanox/mlx4/qp.c
@@ -55,7 +55,7 @@ void mlx4_qp_event(struct mlx4_dev *dev, u32 qpn, int event_type)
 
        qp = __mlx4_qp_lookup(dev, qpn);
        if (qp)
-               atomic_inc(&qp->refcount);
+               refcount_inc(&qp->refcount);
 
        spin_unlock(&qp_table->lock);
 
@@ -66,7 +66,7 @@ void mlx4_qp_event(struct mlx4_dev *dev, u32 qpn, int event_type)
 
        qp->event(qp, event_type);
 
-       if (atomic_dec_and_test(&qp->refcount))
+       if (refcount_dec_and_test(&qp->refcount))
                complete(&qp->free);
 }
 
@@ -420,7 +420,7 @@ int mlx4_qp_alloc(struct mlx4_dev *dev, int qpn, struct mlx4_qp *qp)
        if (err)
                goto err_icm;
 
-       atomic_set(&qp->refcount, 1);
+       refcount_set(&qp->refcount, 1);
        init_completion(&qp->free);
 
        return 0;
@@ -520,7 +520,7 @@ EXPORT_SYMBOL_GPL(mlx4_qp_remove);
 
 void mlx4_qp_free(struct mlx4_dev *dev, struct mlx4_qp *qp)
 {
-       if (atomic_dec_and_test(&qp->refcount))
+       if (refcount_dec_and_test(&qp->refcount))
                complete(&qp->free);
        wait_for_completion(&qp->free);
 

diff --git a/include/linux/mlx4/device.h b/include/linux/mlx4/device.h
index daac2e3a1a58035c0a28d8ce9bf71eb584b68e33..b8e19c4d6caafd89e613c81560fc9ee87f27f868 100644 (file)
--- a/include/linux/mlx4/device.h
+++ b/include/linux/mlx4/device.h
@@ -768,7 +768,7 @@ struct mlx4_qp {
 
        int                     qpn;
 
-       atomic_t                refcount;
+       refcount_t              refcount;
        struct completion       free;
        u8                      usage;
 };