[PATCH 05/23] net, ceph: convert ceph_osd.o_ref from atomic_t to refcount_t

[Elena Reshetova]

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.reshet...@intel.com>
Signed-off-by: Hans Liljestrand <ishkam...@gmail.com>
Signed-off-by: Kees Cook <keesc...@chromium.org>
Signed-off-by: David Windsor <dwind...@gmail.com>
---
 include/linux/ceph/osd_client.h |  3 ++-
 net/ceph/osd_client.c           | 16 ++++++++--------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
index 2ea0c28..5ce0cd6 100644
--- a/include/linux/ceph/osd_client.h
+++ b/include/linux/ceph/osd_client.h
@@ -5,6 +5,7 @@
 #include <linux/kref.h>
 #include <linux/mempool.h>
 #include <linux/rbtree.h>
+#include <linux/refcount.h>
 
 #include <linux/ceph/types.h>
 #include <linux/ceph/osdmap.h>
@@ -27,7 +28,7 @@ typedef void (*ceph_osdc_callback_t)(struct ceph_osd_request 
*);
 
 /* a given osd we're communicating with */
 struct ceph_osd {
-       atomic_t o_ref;
+       refcount_t o_ref;
        struct ceph_osd_client *o_osdc;
        int o_osd;
        int o_incarnation;
diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index b65bbf9..99a51f0 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -1005,7 +1005,7 @@ static bool osd_registered(struct ceph_osd *osd)
  */
 static void osd_init(struct ceph_osd *osd)
 {
-       atomic_set(&osd->o_ref, 1);
+       refcount_set(&osd->o_ref, 1);
        RB_CLEAR_NODE(&osd->o_node);
        osd->o_requests = RB_ROOT;
        osd->o_linger_requests = RB_ROOT;
@@ -1050,9 +1050,9 @@ static struct ceph_osd *create_osd(struct ceph_osd_client 
*osdc, int onum)
 
 static struct ceph_osd *get_osd(struct ceph_osd *osd)
 {
-       if (atomic_inc_not_zero(&osd->o_ref)) {
-               dout("get_osd %p %d -> %d\n", osd, atomic_read(&osd->o_ref)-1,
-                    atomic_read(&osd->o_ref));
+       if (refcount_inc_not_zero(&osd->o_ref)) {
+               dout("get_osd %p %d -> %d\n", osd, refcount_read(&osd->o_ref)-1,
+                    refcount_read(&osd->o_ref));
                return osd;
        } else {
                dout("get_osd %p FAIL\n", osd);
@@ -1062,9 +1062,9 @@ static struct ceph_osd *get_osd(struct ceph_osd *osd)
 
 static void put_osd(struct ceph_osd *osd)
 {
-       dout("put_osd %p %d -> %d\n", osd, atomic_read(&osd->o_ref),
-            atomic_read(&osd->o_ref) - 1);
-       if (atomic_dec_and_test(&osd->o_ref)) {
+       dout("put_osd %p %d -> %d\n", osd, refcount_read(&osd->o_ref),
+            refcount_read(&osd->o_ref) - 1);
+       if (refcount_dec_and_test(&osd->o_ref)) {
                osd_cleanup(osd);
                kfree(osd);
        }
@@ -4092,7 +4092,7 @@ void ceph_osdc_stop(struct ceph_osd_client *osdc)
                close_osd(osd);
        }
        up_write(&osdc->lock);
-       WARN_ON(atomic_read(&osdc->homeless_osd.o_ref) != 1);
+       WARN_ON(refcount_read(&osdc->homeless_osd.o_ref) != 1);
        osd_cleanup(&osdc->homeless_osd);
 
        WARN_ON(!list_empty(&osdc->osd_lru));
-- 
2.7.4