drivers, net, mlx5: convert mlx5_cq.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 mlx5_cq.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/mlx5/core/cq.c b/drivers/net/ethernet/mellanox/mlx5/core/cq.c
index 336d473..1016e05 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx5/core/cq.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/cq.c
@@ -58,7 +58,7 @@ void mlx5_cq_tasklet_cb(unsigned long data)
                                 tasklet_ctx.list) {
                list_del_init(&mcq->tasklet_ctx.list);
                mcq->tasklet_ctx.comp(mcq);
-               if (atomic_dec_and_test(&mcq->refcount))
+               if (refcount_dec_and_test(&mcq->refcount))
                        complete(&mcq->free);
                if (time_after(jiffies, end))
                        break;
@@ -80,7 +80,7 @@ static void mlx5_add_cq_to_tasklet(struct mlx5_core_cq *cq)
         * still arrive.
         */
        if (list_empty_careful(&cq->tasklet_ctx.list)) {
-               atomic_inc(&cq->refcount);
+               refcount_inc(&cq->refcount);
                list_add_tail(&cq->tasklet_ctx.list, &tasklet_ctx->list);
        }
        spin_unlock_irqrestore(&tasklet_ctx->lock, flags);
@@ -94,7 +94,7 @@ void mlx5_cq_completion(struct mlx5_core_dev *dev, u32 cqn)
        spin_lock(&table->lock);
        cq = radix_tree_lookup(&table->tree, cqn);
        if (likely(cq))
-               atomic_inc(&cq->refcount);
+               refcount_inc(&cq->refcount);
        spin_unlock(&table->lock);
 
        if (!cq) {
@@ -106,7 +106,7 @@ void mlx5_cq_completion(struct mlx5_core_dev *dev, u32 cqn)
 
        cq->comp(cq);
 
-       if (atomic_dec_and_test(&cq->refcount))
+       if (refcount_dec_and_test(&cq->refcount))
                complete(&cq->free);
 }
 
@@ -119,7 +119,7 @@ void mlx5_cq_event(struct mlx5_core_dev *dev, u32 cqn, int event_type)
 
        cq = radix_tree_lookup(&table->tree, cqn);
        if (cq)
-               atomic_inc(&cq->refcount);
+               refcount_inc(&cq->refcount);
 
        spin_unlock(&table->lock);
 
@@ -130,7 +130,7 @@ void mlx5_cq_event(struct mlx5_core_dev *dev, u32 cqn, int event_type)
 
        cq->event(cq, event_type);
 
-       if (atomic_dec_and_test(&cq->refcount))
+       if (refcount_dec_and_test(&cq->refcount))
                complete(&cq->free);
 }
 
@@ -159,7 +159,7 @@ int mlx5_core_create_cq(struct mlx5_core_dev *dev, struct mlx5_core_cq *cq,
        cq->cqn = MLX5_GET(create_cq_out, out, cqn);
        cq->cons_index = 0;
        cq->arm_sn     = 0;
-       atomic_set(&cq->refcount, 1);
+       refcount_set(&cq->refcount, 1);
        init_completion(&cq->free);
        if (!cq->comp)
                cq->comp = mlx5_add_cq_to_tasklet;
@@ -222,7 +222,7 @@ int mlx5_core_destroy_cq(struct mlx5_core_dev *dev, struct mlx5_core_cq *cq)
        synchronize_irq(cq->irqn);
 
        mlx5_debug_cq_remove(dev, cq);
-       if (atomic_dec_and_test(&cq->refcount))
+       if (refcount_dec_and_test(&cq->refcount))
                complete(&cq->free);
        wait_for_completion(&cq->free);
 

diff --git a/include/linux/mlx5/cq.h b/include/linux/mlx5/cq.h
index 9589884..6a57ec2 100644 (file)
--- a/include/linux/mlx5/cq.h
+++ b/include/linux/mlx5/cq.h
@@ -35,7 +35,7 @@
 
 #include <rdma/ib_verbs.h>
 #include <linux/mlx5/driver.h>
-
+#include <linux/refcount.h>
 
 struct mlx5_core_cq {
        u32                     cqn;
@@ -43,7 +43,7 @@ struct mlx5_core_cq {
        __be32                 *set_ci_db;
        __be32                 *arm_db;
        struct mlx5_uars_page  *uar;
-       atomic_t                refcount;
+       refcount_t              refcount;
        struct completion       free;
        unsigned                vector;
        unsigned int            irqn;