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drivers, net, mlx4: convert mlx4_qp.refcount from atomic_t to refcount_t

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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@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>
This commit is contained in:
Elena Reshetova 2017-10-20 10:23:38 +03:00 committed by David S. Miller
parent ff61b5e3f0
commit 0068895ff8
2 changed files with 5 additions and 5 deletions
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8
drivers/net/ethernet/mellanox/mlx4/qp.c
View File

@ -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);

2
include/linux/mlx4/device.h
View File

@ -768,7 +768,7 @@ struct mlx4_qp {
int qpn;
atomic_t refcount;
refcount_t refcount;
struct completion free;
u8 usage;
};