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_cq.refcount is used as pure reference counter.
Convert it to refcount_t and fix up the operations.
Suggested-by: Kees Cook <keesc...@chromium.org>
Reviewed-by: David Windsor <dwind...@gmail.com>
Reviewed-by: Hans Liljestrand <ishkam...@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshet...@intel.com>
---
drivers/net/ethernet/mellanox/mlx4/cq.c | 8 ++++----
include/linux/mlx4/device.h | 4 ++--
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlx4/cq.c
b/drivers/net/ethernet/mellanox/mlx4/cq.c
index 72eb50c..d8e9a32 100644
--- a/drivers/net/ethernet/mellanox/mlx4/cq.c
+++ b/drivers/net/ethernet/mellanox/mlx4/cq.c
@@ -69,7 +69,7 @@ void mlx4_cq_tasklet_cb(unsigned long data)
list_for_each_entry_safe(mcq, temp, &ctx->process_list,
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;
@@ -92,7 +92,7 @@ static void mlx4_add_cq_to_tasklet(struct mlx4_cq *cq)
* still arrive.
*/
if (list_empty_careful(&cq->tasklet_ctx.list)) {
- atomic_inc(&cq->refcount);
+ refcount_inc(&cq->refcount);
kick = list_empty(&tasklet_ctx->list);
list_add_tail(&cq->tasklet_ctx.list, &tasklet_ctx->list);
if (kick)
@@ -344,7 +344,7 @@ int mlx4_cq_alloc(struct mlx4_dev *dev, int nent,
cq->cons_index = 0;
cq->arm_sn = 1;
cq->uar = uar;
- atomic_set(&cq->refcount, 1);
+ refcount_set(&cq->refcount, 1);
init_completion(&cq->free);
cq->comp = mlx4_add_cq_to_tasklet;
cq->tasklet_ctx.priv =
@@ -386,7 +386,7 @@ void mlx4_cq_free(struct mlx4_dev *dev, struct mlx4_cq *cq)
priv->eq_table.eq[MLX4_EQ_ASYNC].irq)
synchronize_irq(priv->eq_table.eq[MLX4_EQ_ASYNC].irq);
- 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/mlx4/device.h b/include/linux/mlx4/device.h
index b0a57e0..daac2e3 100644
--- a/include/linux/mlx4/device.h
+++ b/include/linux/mlx4/device.h
@@ -40,7 +40,7 @@
#include <linux/cpu_rmap.h>
#include <linux/crash_dump.h>
-#include <linux/atomic.h>
+#include <linux/refcount.h>
#include <linux/timecounter.h>
@@ -751,7 +751,7 @@ struct mlx4_cq {
int cqn;
unsigned vector;
- atomic_t refcount;
+ refcount_t refcount;
struct completion free;
struct {
struct list_head list;
--
2.7.4
