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