drivers, net, mlx5: convert mlx5_cq.refcount from atomic_t to refcount_t
authorElena Reshetova <elena.reshetova@intel.com>
Fri, 20 Oct 2017 07:23:40 +0000 (10:23 +0300)
committerDavid S. Miller <davem@davemloft.net>
Sun, 22 Oct 2017 01:22:38 +0000 (02:22 +0100)
commita4b51a9f83c6d359ff8fc0c66009283b6fdeeaf8
tree4f39360cf6abe522b6ab22e7bc419fadf391c318
parent17ac99b2b8d08ed40f4525491d6eff330329a6d2
drivers, net, mlx5: convert mlx5_cq.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 mlx5_cq.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>
drivers/net/ethernet/mellanox/mlx5/core/cq.c
include/linux/mlx5/cq.h