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>
---
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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