ceph: convert ceph_mds_session.s_ref from atomic_t to refcount_t

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@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index c681762d76e66be1edf7004b1de8c13568ec6022..074490542b4ce39ac3b6d56f88c453b05cda0281 100644 (file)
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -378,9 +378,9 @@ const char *ceph_session_state_name(int s)
 
 static struct ceph_mds_session *get_session(struct ceph_mds_session *s)
 {
-       if (atomic_inc_not_zero(&s->s_ref)) {
+       if (refcount_inc_not_zero(&s->s_ref)) {
                dout("mdsc get_session %p %d -> %d\n", s,
-                    atomic_read(&s->s_ref)-1, atomic_read(&s->s_ref));
+                    refcount_read(&s->s_ref)-1, refcount_read(&s->s_ref));
                return s;
        } else {
                dout("mdsc get_session %p 0 -- FAIL", s);
@@ -391,8 +391,8 @@ static struct ceph_mds_session *get_session(struct ceph_mds_session *s)
 void ceph_put_mds_session(struct ceph_mds_session *s)
 {
        dout("mdsc put_session %p %d -> %d\n", s,
-            atomic_read(&s->s_ref), atomic_read(&s->s_ref)-1);
-       if (atomic_dec_and_test(&s->s_ref)) {
+            refcount_read(&s->s_ref), refcount_read(&s->s_ref)-1);
+       if (refcount_dec_and_test(&s->s_ref)) {
                if (s->s_auth.authorizer)
                        ceph_auth_destroy_authorizer(s->s_auth.authorizer);
                kfree(s);
@@ -411,7 +411,7 @@ struct ceph_mds_session *__ceph_lookup_mds_session(struct ceph_mds_client *mdsc,
                return NULL;
        session = mdsc->sessions[mds];
        dout("lookup_mds_session %p %d\n", session,
-            atomic_read(&session->s_ref));
+            refcount_read(&session->s_ref));
        get_session(session);
        return session;
 }
@@ -466,7 +466,7 @@ static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
        INIT_LIST_HEAD(&s->s_caps);
        s->s_nr_caps = 0;
        s->s_trim_caps = 0;
-       atomic_set(&s->s_ref, 1);
+       refcount_set(&s->s_ref, 1);
        INIT_LIST_HEAD(&s->s_waiting);
        INIT_LIST_HEAD(&s->s_unsafe);
        s->s_num_cap_releases = 0;
@@ -494,7 +494,7 @@ static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
        }
        mdsc->sessions[mds] = s;
        atomic_inc(&mdsc->num_sessions);
-       atomic_inc(&s->s_ref);  /* one ref to sessions[], one to caller */
+       refcount_inc(&s->s_ref);  /* one ref to sessions[], one to caller */
 
        ceph_con_open(&s->s_con, CEPH_ENTITY_TYPE_MDS, mds,
                      ceph_mdsmap_get_addr(mdsc->mdsmap, mds));
@@ -3881,7 +3881,7 @@ static struct ceph_connection *con_get(struct ceph_connection *con)
        struct ceph_mds_session *s = con->private;
 
        if (get_session(s)) {
-               dout("mdsc con_get %p ok (%d)\n", s, atomic_read(&s->s_ref));
+               dout("mdsc con_get %p ok (%d)\n", s, refcount_read(&s->s_ref));
                return con;
        }
        dout("mdsc con_get %p FAIL\n", s);
@@ -3892,7 +3892,7 @@ static void con_put(struct ceph_connection *con)
 {
        struct ceph_mds_session *s = con->private;
 
-       dout("mdsc con_put %p (%d)\n", s, atomic_read(&s->s_ref) - 1);
+       dout("mdsc con_put %p (%d)\n", s, refcount_read(&s->s_ref) - 1);
        ceph_put_mds_session(s);
 }
 

diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index ac0475a2daa749d3d689956cc45a2913c955ca8f..bbebcd55d79e89dd86e62dffa6ada0ed000fa0c5 100644 (file)
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -7,6 +7,7 @@
 #include <linux/mutex.h>
 #include <linux/rbtree.h>
 #include <linux/spinlock.h>
+#include <linux/refcount.h>
 
 #include <linux/ceph/types.h>
 #include <linux/ceph/messenger.h>
@@ -156,7 +157,7 @@ struct ceph_mds_session {
        unsigned long     s_renew_requested; /* last time we sent a renew req */
        u64               s_renew_seq;
 
-       atomic_t          s_ref;
+       refcount_t          s_ref;
        struct list_head  s_waiting;  /* waiting requests */
        struct list_head  s_unsafe;   /* unsafe requests */
 };
@@ -373,7 +374,7 @@ __ceph_lookup_mds_session(struct ceph_mds_client *, int mds);
 static inline struct ceph_mds_session *
 ceph_get_mds_session(struct ceph_mds_session *s)
 {
-       atomic_inc(&s->s_ref);
+       refcount_inc(&s->s_ref);
        return s;
 }