static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
{
	key_t key = params->key;
	int shmflg = params->flg;
	size_t size = params->u.size;
	int error;
	struct shmid_kernel *shp;
	size_t numpages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
	struct file *file;
	char name[13];
	int id;
	vm_flags_t acctflag = 0;

	if (size < SHMMIN || size > ns->shm_ctlmax)
		return -EINVAL;

	if (numpages << PAGE_SHIFT < size)
		return -ENOSPC;

	if (ns->shm_tot + numpages < ns->shm_tot ||
			ns->shm_tot + numpages > ns->shm_ctlall)
		return -ENOSPC;

	shp = ipc_rcu_alloc(sizeof(*shp));
	if (!shp)
		return -ENOMEM;

	shp->shm_perm.key = key;
	shp->shm_perm.mode = (shmflg & S_IRWXUGO);
	shp->mlock_user = NULL;

	shp->shm_perm.security = NULL;
	error = security_shm_alloc(shp);
	if (error) {
		ipc_rcu_putref(shp, ipc_rcu_free);
		return error;
	}

	sprintf(name, "SYSV%08x", key);
	if (shmflg & SHM_HUGETLB) {
		struct hstate *hs;
		size_t hugesize;

		hs = hstate_sizelog((shmflg >> SHM_HUGE_SHIFT) & SHM_HUGE_MASK);
		if (!hs) {
			error = -EINVAL;
			goto no_file;
		}
		hugesize = ALIGN(size, huge_page_size(hs));

		/* hugetlb_file_setup applies strict accounting */
		if (shmflg & SHM_NORESERVE)
			acctflag = VM_NORESERVE;
		file = hugetlb_file_setup(name, hugesize, acctflag,
				  &shp->mlock_user, HUGETLB_SHMFS_INODE,
				(shmflg >> SHM_HUGE_SHIFT) & SHM_HUGE_MASK);
	} else {
		/*
		 * Do not allow no accounting for OVERCOMMIT_NEVER, even
		 * if it's asked for.
		 */
		if  ((shmflg & SHM_NORESERVE) &&
				sysctl_overcommit_memory != OVERCOMMIT_NEVER)
			acctflag = VM_NORESERVE;
		file = shmem_kernel_file_setup(name, size, acctflag);
	}
	error = PTR_ERR(file);
 	if (IS_ERR(file))
 		goto no_file;
 
	id = ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni);
	if (id < 0) {
		error = id;
		goto no_id;
	}
 	shp->shm_cprid = task_tgid_vnr(current);
 	shp->shm_lprid = 0;
 	shp->shm_atim = shp->shm_dtim = 0;
	shp->shm_ctim = get_seconds();
	shp->shm_segsz = size;
 	shp->shm_nattch = 0;
 	shp->shm_file = file;
 	shp->shm_creator = current;
 	list_add(&shp->shm_clist, &current->sysvshm.shm_clist);
 
 	/*
	 * shmid gets reported as "inode#" in /proc/pid/maps.
	 * proc-ps tools use this. Changing this will break them.
	 */
	file_inode(file)->i_ino = shp->shm_perm.id;

	ns->shm_tot += numpages;
	error = shp->shm_perm.id;

	ipc_unlock_object(&shp->shm_perm);
	rcu_read_unlock();
	return error;

no_id:
	if (is_file_hugepages(file) && shp->mlock_user)
		user_shm_unlock(size, shp->mlock_user);
	fput(file);
no_file:
	ipc_rcu_putref(shp, shm_rcu_free);
	return error;
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.