From 6dc18fee972234ca7964f5ca7ec0ac76f8b8f5e9 Mon Sep 17 00:00:00 2001
From: Pavel Emelyanov <xemul@openvz.org>
Date: Wed, 28 Nov 2007 16:21:39 -0800
Subject: [PATCH] --- yaml --- r: 74363 b: refs/heads/master c:
 2868f89fc43d16441a90714d4676089bdfc4255a h: refs/heads/master i:   74361:
 35bd99da7149f0d423def99edc018fd09c35dad9   74359:
 4d9291990d13cce9acd84aa136ff5cf834b97b5f v: v3

---
 [refs]                                        |  2 +-
 trunk/Documentation/00-INDEX                  |  2 +
 .../namespaces/compatibility-list.txt         | 39 +++++++++++++++++++
 3 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 trunk/Documentation/namespaces/compatibility-list.txt

diff --git a/[refs] b/[refs]
index fc275376543f..7f86909fc300 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 32df81cbd5b41d281cc3d7e7ff6a98ac6201e197
+refs/heads/master: 2868f89fc43d16441a90714d4676089bdfc4255a
diff --git a/trunk/Documentation/00-INDEX b/trunk/Documentation/00-INDEX
index 299615d821ac..c3014df066c4 100644
--- a/trunk/Documentation/00-INDEX
+++ b/trunk/Documentation/00-INDEX
@@ -262,6 +262,8 @@ mtrr.txt
 	- how to use PPro Memory Type Range Registers to increase performance.
 mutex-design.txt
 	- info on the generic mutex subsystem.
+namespaces/
+	- directory with various information about namespaces
 nbd.txt
 	- info on a TCP implementation of a network block device.
 netlabel/
diff --git a/trunk/Documentation/namespaces/compatibility-list.txt b/trunk/Documentation/namespaces/compatibility-list.txt
new file mode 100644
index 000000000000..defc5589bfcd
--- /dev/null
+++ b/trunk/Documentation/namespaces/compatibility-list.txt
@@ -0,0 +1,39 @@
+	Namespaces compatibility list
+
+This document contains the information about the problems user
+may have when creating tasks living in different namespaces.
+
+Here's the summary. This matrix shows the known problems, that
+occur when tasks share some namespace (the columns) while living
+in different other namespaces (the rows):
+
+	UTS	IPC	VFS	PID	User	Net
+UTS	 X
+IPC		 X	 1
+VFS			 X
+PID		 1	 1	 X
+User		 2	 2		 X
+Net						 X
+
+1. Both the IPC and the PID namespaces provide IDs to address
+   object inside the kernel. E.g. semaphore with IPCID or
+   process group with pid.
+
+   In both cases, tasks shouldn't try exposing this ID to some
+   other task living in a different namespace via a shared filesystem
+   or IPC shmem/message. The fact is that this ID is only valid
+   within the namespace it was obtained in and may refer to some
+   other object in another namespace.
+
+2. Intentionally, two equal user IDs in different user namespaces
+   should not be equal from the VFS point of view. In other
+   words, user 10 in one user namespace shouldn't have the same
+   access permissions to files, belonging to user 10 in another
+   namespace.
+
+   The same is true for the IPC namespaces being shared - two users
+   from different user namespaces should not access the same IPC objects
+   even having equal UIDs.
+
+   But currently this is not so.
+