Re: [Xen-devel] [PATCH 22/29] drivers, scsi: convert iscsi_task.refcount from atomic_t to refcount_t

[Chris Leech <cleech@xxxxxxxxxx>]

On Mon, Mar 06, 2017 at 04:21:09PM +0200, Elena Reshetova wrote:
> refcount_t type and corresponding API should be
> used instead of atomic_t when the variable is used as
> a reference counter. This allows to avoid accidental
> refcounter overflows that might lead to use-after-free
> situations.
> 
> Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
> Signed-off-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Signed-off-by: David Windsor <dwindsor@xxxxxxxxx>

This looks OK to me.

Acked-by: Chris Leech <cleech@xxxxxxxxxx>

> ---
>  drivers/scsi/libiscsi.c        | 8 ++++----
>  drivers/scsi/qedi/qedi_iscsi.c | 2 +-
>  include/scsi/libiscsi.h        | 3 ++-
>  3 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
> index 834d121..7eb1d2c 100644
> --- a/drivers/scsi/libiscsi.c
> +++ b/drivers/scsi/libiscsi.c
> @@ -516,13 +516,13 @@ static void iscsi_free_task(struct iscsi_task *task)
>  
>  void __iscsi_get_task(struct iscsi_task *task)
>  {
> -     atomic_inc(&task->refcount);
> +     refcount_inc(&task->refcount);
>  }
>  EXPORT_SYMBOL_GPL(__iscsi_get_task);
>  
>  void __iscsi_put_task(struct iscsi_task *task)
>  {
> -     if (atomic_dec_and_test(&task->refcount))
> +     if (refcount_dec_and_test(&task->refcount))
>               iscsi_free_task(task);
>  }
>  EXPORT_SYMBOL_GPL(__iscsi_put_task);
> @@ -744,7 +744,7 @@ __iscsi_conn_send_pdu(struct iscsi_conn *conn, struct 
> iscsi_hdr *hdr,
>        * released by the lld when it has transmitted the task for
>        * pdus we do not expect a response for.
>        */
> -     atomic_set(&task->refcount, 1);
> +     refcount_set(&task->refcount, 1);
>       task->conn = conn;
>       task->sc = NULL;
>       INIT_LIST_HEAD(&task->running);
> @@ -1616,7 +1616,7 @@ static inline struct iscsi_task 
> *iscsi_alloc_task(struct iscsi_conn *conn,
>       sc->SCp.phase = conn->session->age;
>       sc->SCp.ptr = (char *) task;
>  
> -     atomic_set(&task->refcount, 1);
> +     refcount_set(&task->refcount, 1);
>       task->state = ISCSI_TASK_PENDING;
>       task->conn = conn;
>       task->sc = sc;
> diff --git a/drivers/scsi/qedi/qedi_iscsi.c b/drivers/scsi/qedi/qedi_iscsi.c
> index b9f79d3..3895bd5 100644
> --- a/drivers/scsi/qedi/qedi_iscsi.c
> +++ b/drivers/scsi/qedi/qedi_iscsi.c
> @@ -1372,7 +1372,7 @@ static void qedi_cleanup_task(struct iscsi_task *task)
>  {
>       if (!task->sc || task->state == ISCSI_TASK_PENDING) {
>               QEDI_INFO(NULL, QEDI_LOG_IO, "Returning ref_cnt=%d\n",
> -                       atomic_read(&task->refcount));
> +                       refcount_read(&task->refcount));
>               return;
>       }
>  
> diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h
> index b0e275d..24d74b5 100644
> --- a/include/scsi/libiscsi.h
> +++ b/include/scsi/libiscsi.h
> @@ -29,6 +29,7 @@
>  #include <linux/timer.h>
>  #include <linux/workqueue.h>
>  #include <linux/kfifo.h>
> +#include <linux/refcount.h>
>  #include <scsi/iscsi_proto.h>
>  #include <scsi/iscsi_if.h>
>  #include <scsi/scsi_transport_iscsi.h>
> @@ -139,7 +140,7 @@ struct iscsi_task {
>  
>       /* state set/tested under session->lock */
>       int                     state;
> -     atomic_t                refcount;
> +     refcount_t              refcount;
>       struct list_head        running;        /* running cmd list */
>       void                    *dd_data;       /* driver/transport data */
>  };
> -- 
> 2.7.4
> 

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