userns: use refcount_t for reference counting instead atomic_t
refcount_t type and corresponding API should be used instead of atomic_t
wh en the variable is used as a reference counter. This avoids accidental
refcounter overflows that might lead to use-after-free situations.
Link: http://lkml.kernel.org/r/20180703200141.28415-6-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/user.c b/kernel/user.c
index 36288d8..5f65ef1 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -96,7 +96,7 @@ 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,
@@ -123,7 +123,7 @@ 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;
}
}
@@ -170,7 +170,7 @@ 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);
@@ -191,7 +191,7 @@ struct user_struct *alloc_uid(kuid_t uid)
goto out_unlock;
new->uid = uid;
- atomic_set(&new->__count, 1);
+ refcount_set(&new->__count, 1);
ratelimit_state_init(&new->ratelimit, HZ, 100);
ratelimit_set_flags(&new->ratelimit, RATELIMIT_MSG_ON_RELEASE);