RE: [PATCH for-next 1/6] RDMA/core: Use refcount_t instead of atomic_t for reference counting

["Saleem, Shiraz" <shiraz.saleem@intel.com>]

> Subject: [PATCH for-next 1/6] RDMA/core: Use refcount_t instead of atomic_t for
> reference counting
> 
> The refcount_t API will WARN on underflow and overflow of a reference counter,
> and avoid use-after-free risks. Increase refcount_t from 0 to 1 is regarded as there
> is a risk about use-after-free. So it should be set to 1 directly during initialization.
> 
> Signed-off-by: Weihang Li <liweihang@huawei.com>
> ---
>  drivers/infiniband/core/iwcm.c        |  9 ++++-----
>  drivers/infiniband/core/iwcm.h        |  2 +-
>  drivers/infiniband/core/iwpm_util.c   | 12 ++++++++----
>  drivers/infiniband/core/iwpm_util.h   |  2 +-
>  drivers/infiniband/core/mad_priv.h    |  2 +-
>  drivers/infiniband/core/multicast.c   | 30 +++++++++++++++---------------
>  drivers/infiniband/core/uverbs.h      |  2 +-
>  drivers/infiniband/core/uverbs_main.c | 12 ++++++------
>  8 files changed, 37 insertions(+), 34 deletions(-)
> 

[...]

> @@ -589,9 +589,9 @@ static struct mcast_group *acquire_group(struct
> mcast_port *port,
>  		kfree(group);
>  		group = cur_group;
>  	} else
> -		atomic_inc(&port->refcount);
> +		refcount_inc(&port->refcount);
>  found:
> -	atomic_inc(&group->refcount);
> +	refcount_inc(&group->refcount);

Seems like there is refcount_inc with refcount = 0 when the group is first created?

>  	spin_unlock_irqrestore(&port->lock, flags);
>  	return group;
>  }