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[PATCH 2/3] ipc: convert sem_undo_list.refcnt from atomic_t to refcount_t

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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>
---
 ipc/sem.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/ipc/sem.c b/ipc/sem.c
index 9e70cd7..d3ab140 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 (;;) {
-- 
2.7.4

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Thread

[PATCH 0/3]  v2 ipc subsystem refcount coversions Elena Reshetova <elena.reshetova@intel.com> - 2017-07-07 11:10 +0200
  [PATCH 1/3] ipc: convert ipc_namespace.count from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-07 11:10 +0200
    Re: [PATCH 1/3] ipc: convert ipc_namespace.count from atomic_t to refcount_t ebiederm@xmission.com (Eric W. Biederman) - 2017-07-10 00:10 +0200
      RE: [PATCH 1/3] ipc: convert ipc_namespace.count from atomic_t to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-07-10 08:50 +0200
        Re: [PATCH 1/3] ipc: convert ipc_namespace.count from atomic_t to refcount_t ebiederm@xmission.com (Eric W. Biederman) - 2017-07-10 10:50 +0200
          Re: [PATCH 1/3] ipc: convert ipc_namespace.count from atomic_t to refcount_t Alexey Dobriyan <adobriyan@gmail.com> - 2017-07-10 11:40 +0200
            Re: [PATCH 1/3] ipc: convert ipc_namespace.count from atomic_t to refcount_t ebiederm@xmission.com (Eric W. Biederman) - 2017-07-10 13:30 +0200
          RE: [PATCH 1/3] ipc: convert ipc_namespace.count from atomic_t to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-07-10 12:00 +0200
            Re: [PATCH 1/3] ipc: convert ipc_namespace.count from atomic_t to refcount_t ebiederm@xmission.com (Eric W. Biederman) - 2017-07-10 13:40 +0200
              RE: [PATCH 1/3] ipc: convert ipc_namespace.count from atomic_t to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-07-10 14:20 +0200
                Re: [PATCH 1/3] ipc: convert ipc_namespace.count from atomic_t to refcount_t ebiederm@xmission.com (Eric W. Biederman) - 2017-07-10 22:50 +0200
                RE: [PATCH 1/3] ipc: convert ipc_namespace.count from atomic_t to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-07-12 11:30 +0200
  [PATCH 2/3] ipc: convert sem_undo_list.refcnt from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-07 11:10 +0200
  [PATCH 3/3] ipc: convert kern_ipc_perm.refcount from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-07-07 11:10 +0200

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