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Documentation / namespaces / compatibility-list.txt

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Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.

1		Namespaces compatibility list
3	This document contains the information about the problems user
4	may have when creating tasks living in different namespaces.
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):
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
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.
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.
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.
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.
38	   But currently this is not so.
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