[Devel] [patch -mm 10/17] nsproxy: add unshare_ns and bind_ns syscalls

[Daniel Lezcano]

Dmitry Mishin wrote:
> On Tuesday 05 December 2006 13:28, clg at fr.ibm.com wrote:
>> From: Cedric Le Goater <clg at fr.ibm.com>
> [skip]
>> +static int switch_ns(int id, unsigned long flags)
>> +{
>> +	int err = 0;
>> +	struct nsproxy *ns = NULL, *old_ns = NULL, *new_ns = NULL;
>> +
>> +	if (flags & ~NS_ALL)
>> +		return -EINVAL;
>> +
>> +	/* Let 0 be a default value ? */
>> +	if (!flags)
>> +		flags = NS_ALL;
>> +
>> +	if (id < 0) {
>> +		struct task_struct *p;
>> +
>> +		err = -ESRCH;
>> +		read_lock(&tasklist_lock);
>> +		p = find_task_by_pid(-id);
>> +		if (p) {
>> +			task_lock(p);
>> +			get_nsproxy(p->nsproxy);
>> +			ns = p->nsproxy;
>> +			task_unlock(p);
>> +		}
>> +		read_unlock(&tasklist_lock);
>> +	} else {
>> +		err = -ENOENT;
>> +		spin_lock_irq(&ns_hash_lock);
>> +		ns = ns_hash_find(id);
>> +		spin_unlock_irq(&ns_hash_lock);
>> +	}
>> +
>> +	if (!ns)
>> +		goto out;
>> +
>> +	new_ns = ns;
>> +
>> +	/*
>> +	 * clone current nsproxy and populate it with the namespaces
>> +	 * chosen by flags.
>> +	 */
>> +	if (flags != NS_ALL) {
>> +		new_ns = dup_namespaces(current->nsproxy);
>> +		if (!new_ns) {
>> +			err = -ENOMEM;
>> +			goto out_ns;
>> +		}
>> +
>> +		if (flags & NS_MNT) {
>> +			put_mnt_ns(new_ns->mnt_ns);
>> +			get_mnt_ns(ns->mnt_ns);
>> +			new_ns->mnt_ns = ns->mnt_ns;
>> +		}
>> +
>> +		if (flags & NS_UTS) {
>> +			put_uts_ns(new_ns->uts_ns);
>> +			get_uts_ns(ns->uts_ns);
>> +			new_ns->uts_ns = ns->uts_ns;
>> +		}
>> +
>> +		if (flags & NS_IPC) {
>> +			put_ipc_ns(new_ns->ipc_ns);
>> +			new_ns->ipc_ns = get_ipc_ns(ns->ipc_ns);
>> +		}
> <<<< This code looks useless for me, as at this time new_ns->any_ptr == 
> ns->any_ptr.

Yep. Because of the kmemdup in clone_namespace called by dup_namespace.