ipc: convert sem_undo_list.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.

Link: http://lkml.kernel.org/r/1499417992-3238-3-git-send-email-elena.reshetova@intel.com
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>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: <arozansk@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/ipc/sem.c b/ipc/sem.c
index c6c50370504c..31b138b9e756 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -122,7 +122,7 @@ struct sem_undo {
  * that may be shared among all a CLONE_SYSVSEM task group.
  */
 struct sem_undo_list {
-        atomic_t                refcnt;
+        refcount_t              refcnt;
         spinlock_t              lock;
         struct list_head        list_proc;
 };
@@ -1642,7 +1642,7 @@ static inline int get_undo_list(struct sem_undo_list **undo_listp)
                 if (undo_list == NULL)
                         return -ENOMEM;
                 spin_lock_init(&undo_list->lock);
-                atomic_set(&undo_list->refcnt, 1);
+                refcount_set(&undo_list->refcnt, 1);
                 INIT_LIST_HEAD(&undo_list->list_proc);
 
                 current->sysvsem.undo_list = undo_list;
@@ -2041,7 +2041,7 @@ int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
                 error = get_undo_list(&undo_list);
                 if (error)
                         return error;
-                atomic_inc(&undo_list->refcnt);
+                refcount_inc(&undo_list->refcnt);
                 tsk->sysvsem.undo_list = undo_list;
         } else
                 tsk->sysvsem.undo_list = NULL;
@@ -2070,7 +2070,7 @@ void exit_sem(struct task_struct *tsk)
                 return;
         tsk->sysvsem.undo_list = NULL;
 
-        if (!atomic_dec_and_test(&ulp->refcnt))
+        if (!refcount_dec_and_test(&ulp->refcnt))
                 return;
 
         for (;;) {