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@xxxxxxxxxxxx>
Reviewed-by: David Windsor <dwindsor@xxxxxxxxx>
Reviewed-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
---
drivers/net/ethernet/mellanox/mlx4/qp.c | 8 ++++----
include/linux/mlx4/device.h | 2 +-
2 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlx4/qp.c b/drivers/net/ethernet/mellanox/mlx4/qp.c
index 2033209..769598f 100644
--- 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 daac2e3..b8e19c4 100644
--- 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;
};
--
2.7.4
--
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