[PATCH linux-cr] nsproxy: record ambient namespaces

["Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

The nsproxy restore path recognizes that an objref of 0 for
ipc or uts ns means don't unshare it.  But the checkpoint side
forgot to write down 0 when the ipc or uts ns isn't unshared!

Fix that.

To test, run a program with a private pidns but shared utsns
which does

	sleep(5);
	sethostname("serge", 6);

checkpoint it, reset your hostname (if you let the program
complete), then restart the program: without this patch, it
will not reset your hostname.  It should, and with this patch
it will.

Signed-off-by: Serge E. Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
---
 kernel/nsproxy.c |   19 +++++++++++++------
 1 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index 0da0d83..dcb502c 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -280,13 +280,20 @@ static int do_checkpoint_ns(struct ckpt_ctx *ctx, struct nsproxy *nsproxy)
 	if (!h)
 		return -ENOMEM;
 
-	ret = checkpoint_obj(ctx, nsproxy->uts_ns, CKPT_OBJ_UTS_NS);
-	if (ret <= 0)
-		goto out;
+	ret = 0;
+	if (nsproxy->uts_ns != ctx->root_nsproxy->uts_ns) {
+		ret = checkpoint_obj(ctx, nsproxy->uts_ns, CKPT_OBJ_UTS_NS);
+		if (ret <= 0)
+			goto out;
+	}
 	h->uts_objref = ret;
-	ret = checkpoint_obj(ctx, nsproxy->ipc_ns, CKPT_OBJ_IPC_NS);
-	if (ret < 0)
-		goto out;
+
+	ret = 0;
+	if (nsproxy->ipc_ns != ctx->root_nsproxy->ipc_ns) {
+		ret = checkpoint_obj(ctx, nsproxy->ipc_ns, CKPT_OBJ_IPC_NS);
+		if (ret < 0)
+			goto out;
+	}
 	h->ipc_objref = ret;
 
 	/* FIXME: for now, only marked visited to pacify leaks */
-- 
1.6.1