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@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/srq.c | 8 ++++----
include/linux/mlx4/device.h | 2 +-
2 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlx4/srq.c b/drivers/net/ethernet/mellanox/mlx4/srq.c
index bedf521..cbe4d97 100644
--- 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 b8e19c4..a9b5fed 100644
--- 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;
};
--
2.7.4
--
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