Quoting Chen Hanxiao (chenhanxiao@xxxxxxxxxxxxxx):
> We could use setns to join the current ns,
> which did a lot of unnecessary work.
> This patch will check this senario and
> return 0 directly.
>
> Signed-off-by: Chen Hanxiao <chenhanxiao@xxxxxxxxxxxxxx>
Plus it's just asking for trouble.
I would ack this, except you need to fclose(file) on the
return paths. So just set err = 0 and goto out.
> ---
> kernel/nsproxy.c | 28 ++++++++++++++++++++++++++++
> 1 file changed, 28 insertions(+)
>
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index ef42d0a..66eea63 100644
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -236,6 +236,34 @@ SYSCALL_DEFINE2(setns, int, fd, int, nstype)
> ops = ei->ns_ops;
> if (nstype && (ops->type != nstype))
> goto out;
> + switch (ops->type) {
> + case CLONE_NEWIPC:
> + if (ei->ns == tsk->nsproxy->ipc_ns)
> + return 0;
> + break;
> + case CLONE_NEWNET:
> + if (ei->ns == tsk->nsproxy->net_ns)
> + return 0;
> + break;
> + case CLONE_NEWNS:
> + if (ei->ns == tsk->nsproxy->mnt_ns)
> + return 0;
> + break;
> + case CLONE_NEWPID:
> + if (ei->ns == tsk->nsproxy->pid_ns_for_children)
> + return 0;
> + break;
> + case CLONE_NEWUSER:
> + if (ei->ns == current_user_ns())
> + return 0;
> + break;
> + case CLONE_NEWUTS:
> + if (ei->ns == tsk->nsproxy->uts_ns)
> + return 0;
> + break;
> + default:
> + goto out;
> + }
>
> new_nsproxy = create_new_namespaces(0, tsk, current_user_ns(), tsk->fs);
> if (IS_ERR(new_nsproxy)) {
> --
> 1.9.0
>
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