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>
---
 drivers/net/hamradio/6pack.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
index 922bf44..ea6c975 100644
--- a/drivers/net/hamradio/6pack.c
+++ b/drivers/net/hamradio/6pack.c
@@ -35,7 +35,7 @@
 #include <linux/tcp.h>
 #include <linux/semaphore.h>
 #include <linux/compat.h>
-#include <linux/atomic.h>
+#include <linux/refcount.h>
 
 #define SIXPACK_VERSION    "Revision: 0.3.0"
 
@@ -120,7 +120,7 @@ struct sixpack {
 
        struct timer_list       tx_t;
        struct timer_list       resync_t;
-       atomic_t                refcnt;
+       refcount_t              refcnt;
        struct semaphore        dead_sem;
        spinlock_t              lock;
 };
@@ -381,7 +381,7 @@ static struct sixpack *sp_get(struct tty_struct *tty)
        read_lock(&disc_data_lock);
        sp = tty->disc_data;
        if (sp)
-               atomic_inc(&sp->refcnt);
+               refcount_inc(&sp->refcnt);
        read_unlock(&disc_data_lock);
 
        return sp;
@@ -389,7 +389,7 @@ static struct sixpack *sp_get(struct tty_struct *tty)
 
 static void sp_put(struct sixpack *sp)
 {
-       if (atomic_dec_and_test(&sp->refcnt))
+       if (refcount_dec_and_test(&sp->refcnt))
                up(&sp->dead_sem);
 }
 
@@ -580,7 +580,7 @@ static int sixpack_open(struct tty_struct *tty)
        sp->dev = dev;
 
        spin_lock_init(&sp->lock);
-       atomic_set(&sp->refcnt, 1);
+       refcount_set(&sp->refcnt, 1);
        sema_init(&sp->dead_sem, 0);
 
        /* !!! length of the buffers. MTU is IP MTU, not PACLEN!  */
@@ -676,7 +676,7 @@ static void sixpack_close(struct tty_struct *tty)
         * We have now ensured that nobody can start using ap from now on, but
         * we have to wait for all existing users to finish.
         */
-       if (!atomic_dec_and_test(&sp->refcnt))
+       if (!refcount_dec_and_test(&sp->refcnt))
                down(&sp->dead_sem);
 
        /* We must stop the queue to avoid potentially scribbling
-- 
2.7.4

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