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drivers, net, mlx4: convert mlx4_srq.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 mlx4_srq.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 10:23:39 +03:00 committed by David S. Miller
parent 0068895ff8
commit 17ac99b2b8
2 changed files with 5 additions and 5 deletions
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8
drivers/net/ethernet/mellanox/mlx4/srq.c
View File

@ -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);

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

@ -781,7 +781,7 @@ struct mlx4_srq {
int max_gs;
int wqe_shift;
atomic_t refcount;
refcount_t refcount;
struct completion free;
};