net, lapb: convert lapb_cb.refcnt 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: David S. Miller <davem@davemloft.net>

2 files changed, 5 insertions, 4 deletions

diff --git a/include/net/lapb.h b/include/net/lapb.h
index 9510f8725f03..85e773742f4e 100644
--- a/include/net/lapb.h
+++ b/include/net/lapb.h
@@ -1,6 +1,7 @@
 #ifndef _LAPB_H
 #define _LAPB_H 
 #include <linux/lapb.h>
+#include <linux/refcount.h>
 
 #define LAPB_HEADER_LEN 20              /* LAPB over Ethernet + a bit more */
 
@@ -101,7 +102,7 @@ struct lapb_cb {
         struct lapb_frame       frmr_data;
         unsigned char           frmr_type;
 
-        atomic_t                refcnt;
+        refcount_t              refcnt;
 };
 
 /* lapb_iface.c */
diff --git a/net/lapb/lapb_iface.c b/net/lapb/lapb_iface.c
index b50b64ac8815..e15314e3b464 100644
--- a/net/lapb/lapb_iface.c
+++ b/net/lapb/lapb_iface.c
@@ -54,12 +54,12 @@ static void lapb_free_cb(struct lapb_cb *lapb)
 
 static __inline__ void lapb_hold(struct lapb_cb *lapb)
 {
-        atomic_inc(&lapb->refcnt);
+        refcount_inc(&lapb->refcnt);
 }
 
 static __inline__ void lapb_put(struct lapb_cb *lapb)
 {
-        if (atomic_dec_and_test(&lapb->refcnt))
+        if (refcount_dec_and_test(&lapb->refcnt))
                 lapb_free_cb(lapb);
 }
 
@@ -136,7 +136,7 @@ static struct lapb_cb *lapb_create_cb(void)
         lapb->mode    = LAPB_DEFAULT_MODE;
         lapb->window  = LAPB_DEFAULT_WINDOW;
         lapb->state   = LAPB_STATE_0;
-        atomic_set(&lapb->refcnt, 1);
+        refcount_set(&lapb->refcnt, 1);
 out:
         return lapb;
 }