drivers, net, mlx4: convert mlx4_srq.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_srq.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/srq.c b/drivers/net/ethernet/mellanox/mlx4/srq.c
index bedf5212682464651fe51d2a12a6ed41a8777f6d..cbe4d9746ddf126d6f15d82e8d7a16761e82708e 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/srq.c
+++ b/drivers/net/ethernet/mellanox/mlx4/srq.c
@@ -49,7 +49,7 @@ void mlx4_srq_event(struct mlx4_dev *dev, u32 srqn, int event_type)
        srq = radix_tree_lookup(&srq_table->tree, srqn & (dev->caps.num_srqs - 1));
        rcu_read_unlock();
        if (srq)
-               atomic_inc(&srq->refcount);
+               refcount_inc(&srq->refcount);
        else {
                mlx4_warn(dev, "Async event for bogus SRQ %08x\n", srqn);
                return;
@@ -57,7 +57,7 @@ void mlx4_srq_event(struct mlx4_dev *dev, u32 srqn, int event_type)
 
        srq->event(srq, event_type);
 
-       if (atomic_dec_and_test(&srq->refcount))
+       if (refcount_dec_and_test(&srq->refcount))
                complete(&srq->free);
 }
 
@@ -203,7 +203,7 @@ int mlx4_srq_alloc(struct mlx4_dev *dev, u32 pdn, u32 cqn, u16 xrcd,
        if (err)
                goto err_radix;
 
-       atomic_set(&srq->refcount, 1);
+       refcount_set(&srq->refcount, 1);
        init_completion(&srq->free);
 
        return 0;
@@ -232,7 +232,7 @@ void mlx4_srq_free(struct mlx4_dev *dev, struct mlx4_srq *srq)
        radix_tree_delete(&srq_table->tree, srq->srqn);
        spin_unlock_irq(&srq_table->lock);
 
-       if (atomic_dec_and_test(&srq->refcount))
+       if (refcount_dec_and_test(&srq->refcount))
                complete(&srq->free);
        wait_for_completion(&srq->free);
 

diff --git a/include/linux/mlx4/device.h b/include/linux/mlx4/device.h
index b8e19c4d6caafd89e613c81560fc9ee87f27f868..a9b5fed8f7c607dc0492b6a8c869a4c82c026296 100644 (file)
--- a/include/linux/mlx4/device.h
+++ b/include/linux/mlx4/device.h
@@ -781,7 +781,7 @@ struct mlx4_srq {
        int                     max_gs;
        int                     wqe_shift;
 
-       atomic_t                refcount;
+       refcount_t              refcount;
        struct completion       free;
 };