diff options
Diffstat (limited to 'Documentation/namespaces/compatibility-list.txt')
-rw-r--r-- | Documentation/namespaces/compatibility-list.txt | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/Documentation/namespaces/compatibility-list.txt b/Documentation/namespaces/compatibility-list.txt new file mode 100644 index 000000000000..defc5589bfcd --- /dev/null +++ b/Documentation/namespaces/compatibility-list.txt | |||
@@ -0,0 +1,39 @@ | |||
1 | Namespaces compatibility list | ||
2 | |||
3 | This document contains the information about the problems user | ||
4 | may have when creating tasks living in different namespaces. | ||
5 | |||
6 | Here's the summary. This matrix shows the known problems, that | ||
7 | occur when tasks share some namespace (the columns) while living | ||
8 | in different other namespaces (the rows): | ||
9 | |||
10 | UTS IPC VFS PID User Net | ||
11 | UTS X | ||
12 | IPC X 1 | ||
13 | VFS X | ||
14 | PID 1 1 X | ||
15 | User 2 2 X | ||
16 | Net X | ||
17 | |||
18 | 1. Both the IPC and the PID namespaces provide IDs to address | ||
19 | object inside the kernel. E.g. semaphore with IPCID or | ||
20 | process group with pid. | ||
21 | |||
22 | In both cases, tasks shouldn't try exposing this ID to some | ||
23 | other task living in a different namespace via a shared filesystem | ||
24 | or IPC shmem/message. The fact is that this ID is only valid | ||
25 | within the namespace it was obtained in and may refer to some | ||
26 | other object in another namespace. | ||
27 | |||
28 | 2. Intentionally, two equal user IDs in different user namespaces | ||
29 | should not be equal from the VFS point of view. In other | ||
30 | words, user 10 in one user namespace shouldn't have the same | ||
31 | access permissions to files, belonging to user 10 in another | ||
32 | namespace. | ||
33 | |||
34 | The same is true for the IPC namespaces being shared - two users | ||
35 | from different user namespaces should not access the same IPC objects | ||
36 | even having equal UIDs. | ||
37 | |||
38 | But currently this is not so. | ||
39 | |||