[PATCH 05/18] net, bluetooth: convert rfcomm_dlc.refcnt 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/net/bluetooth/rfcomm.h | 8 +++++---
 net/bluetooth/rfcomm/core.c    | 4 ++--
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/include/net/bluetooth/rfcomm.h b/include/net/bluetooth/rfcomm.h
index 4190af5..da4acef 100644
--- a/include/net/bluetooth/rfcomm.h
+++ b/include/net/bluetooth/rfcomm.h
@@ -21,6 +21,8 @@
    SOFTWARE IS DISCLAIMED.
 */
 
+#include <linux/refcount.h>
+
 #ifndef __RFCOMM_H
 #define __RFCOMM_H
 
@@ -174,7 +176,7 @@ struct rfcomm_dlc {
        struct mutex  lock;
        unsigned long state;
        unsigned long flags;
-       atomic_t      refcnt;
+       refcount_t    refcnt;
        u8            dlci;
        u8            addr;
        u8            priority;
@@ -247,12 +249,12 @@ struct rfcomm_dlc *rfcomm_dlc_exists(bdaddr_t *src, 
bdaddr_t *dst, u8 channel);
 
 static inline void rfcomm_dlc_hold(struct rfcomm_dlc *d)
 {
-       atomic_inc(&d->refcnt);
+       refcount_inc(&d->refcnt);
 }
 
 static inline void rfcomm_dlc_put(struct rfcomm_dlc *d)
 {
-       if (atomic_dec_and_test(&d->refcnt))
+       if (refcount_dec_and_test(&d->refcnt))
                rfcomm_dlc_free(d);
 }
 
diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
index f7eb02f..8ebca90 100644
--- a/net/bluetooth/rfcomm/core.c
+++ b/net/bluetooth/rfcomm/core.c
@@ -311,7 +311,7 @@ struct rfcomm_dlc *rfcomm_dlc_alloc(gfp_t prio)
 
        skb_queue_head_init(&d->tx_queue);
        mutex_init(&d->lock);
-       atomic_set(&d->refcnt, 1);
+       refcount_set(&d->refcnt, 1);
 
        rfcomm_dlc_clear_state(d);
 
@@ -342,7 +342,7 @@ static void rfcomm_dlc_unlink(struct rfcomm_dlc *d)
 {
        struct rfcomm_session *s = d->session;
 
-       BT_DBG("dlc %p refcnt %d session %p", d, atomic_read(&d->refcnt), s);
+       BT_DBG("dlc %p refcnt %d session %p", d, refcount_read(&d->refcnt), s);
 
        list_del(&d->list);
        d->session = NULL;
-- 
2.7.4