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>
---
include/linux/sched.h | 4 ++--
kernel/user.c | 8 ++++----
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6aad885..e90396f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -844,7 +844,7 @@ static inline int signal_group_exit(const struct
signal_struct *sig)
* Some day this will be a full-fledged user tracking system..
*/
struct user_struct {
- atomic_t __count; /* reference count */
+ refcount_t __count; /* reference count */
atomic_t processes; /* How many processes does this user have? */
atomic_t sigpending; /* How many pending signals does this user
have? */
#ifdef CONFIG_FANOTIFY
@@ -2694,7 +2694,7 @@ extern struct task_struct *find_task_by_pid_ns(pid_t nr,
extern struct user_struct * alloc_uid(kuid_t);
static inline struct user_struct *get_uid(struct user_struct *u)
{
- atomic_inc(&u->__count);
+ refcount_inc(&u->__count);
return u;
}
extern void free_uid(struct user_struct *);
diff --git a/kernel/user.c b/kernel/user.c
index b069ccb..d9dff8e 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -89,7 +89,7 @@ static DEFINE_SPINLOCK(uidhash_lock);
/* root_user.__count is 1, for init task cred */
struct user_struct root_user = {
- .__count = ATOMIC_INIT(1),
+ .__count = REFCOUNT_INIT(1),
.processes = ATOMIC_INIT(1),
.sigpending = ATOMIC_INIT(0),
.locked_shm = 0,
@@ -115,7 +115,7 @@ static struct user_struct *uid_hash_find(kuid_t uid, struct
hlist_head *hashent)
hlist_for_each_entry(user, hashent, uidhash_node) {
if (uid_eq(user->uid, uid)) {
- atomic_inc(&user->__count);
+ refcount_inc(&user->__count);
return user;
}
}
@@ -162,7 +162,7 @@ void free_uid(struct user_struct *up)
return;
local_irq_save(flags);
- if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
+ if (refcount_dec_and_lock(&up->__count, &uidhash_lock))
free_user(up, flags);
else
local_irq_restore(flags);
@@ -183,7 +183,7 @@ struct user_struct *alloc_uid(kuid_t uid)
goto out_unlock;
new->uid = uid;
- atomic_set(&new->__count, 1);
+ refcount_set(&new->__count, 1);
/*
* Before adding this, check whether we raced
--
2.7.4
