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

[Elena Reshetova <elena.reshetova@xxxxxxxxx>]

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>
---
 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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