Code: static noinline void key_gc_unused_keys(struct list_head *keys)
{
	while (!list_empty(keys)) {
		struct key *key =
			list_entry(keys->next, struct key, graveyard_link);
		list_del(&key->graveyard_link);

 		kdebug("- %u", key->serial);
 		key_check(key);
 
		/* Throw away the key data */
		if (key->type->destroy)
 			key->type->destroy(key);
 
 		security_key_free(key);

		/* deal with the user's key tracking and quota */
		if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
			spin_lock(&key->user->lock);
			key->user->qnkeys--;
			key->user->qnbytes -= key->quotalen;
			spin_unlock(&key->user->lock);
		}

		atomic_dec(&key->user->nkeys);
		if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
			atomic_dec(&key->user->nikeys);

		key_user_put(key->user);

		kfree(key->description);

#ifdef KEY_DEBUGGING
		key->magic = KEY_DEBUG_MAGIC_X;
#endif
		kmem_cache_free(key_jar, key);
	}
}

Vulnerability Type: DoS 
CWE ID: CWE-20
Summary: The key_gc_unused_keys function in security/keys/gc.c in the Linux kernel through 4.2.6 allows local users to cause a denial of service (OOPS) via crafted keyctl commands.
Commit Message: Merge branch 'keys-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull key handling fixes from David Howells:
 "Here are two patches, the first of which at least should go upstream
  immediately:

  (1) Prevent a user-triggerable crash in the keyrings destructor when a
      negatively instantiated keyring is garbage collected.  I have also
      seen this triggered for user type keys.

  (2) Prevent the user from using requesting that a keyring be created
      and instantiated through an upcall.  Doing so is probably safe
      since the keyring type ignores the arguments to its instantiation
      function - but we probably shouldn't let keyrings be created in
      this manner"

* 'keys-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  KEYS: Don't permit request_key() to construct a new keyring
  KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring