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20a78ae9ed
Rename the namespaces documentation files to ReST, add an index for them and adjust in order to produce a nice html output via the Sphinx build system. There are two upper case file names. Rename them to lower case, as we're working to avoid upper case file names at Documentation. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
44 lines
1.5 KiB
ReStructuredText
44 lines
1.5 KiB
ReStructuredText
=============================
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Namespaces compatibility list
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=============================
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This document contains the information about the problems user
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may have when creating tasks living in different namespaces.
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Here's the summary. This matrix shows the known problems, that
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occur when tasks share some namespace (the columns) while living
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in different other namespaces (the rows):
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==== === === === === ==== ===
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- UTS IPC VFS PID User Net
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==== === === === === ==== ===
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UTS X
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IPC X 1
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VFS X
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PID 1 1 X
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User 2 2 X
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Net X
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==== === === === === ==== ===
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1. Both the IPC and the PID namespaces provide IDs to address
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object inside the kernel. E.g. semaphore with IPCID or
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process group with pid.
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In both cases, tasks shouldn't try exposing this ID to some
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other task living in a different namespace via a shared filesystem
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or IPC shmem/message. The fact is that this ID is only valid
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within the namespace it was obtained in and may refer to some
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other object in another namespace.
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2. Intentionally, two equal user IDs in different user namespaces
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should not be equal from the VFS point of view. In other
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words, user 10 in one user namespace shouldn't have the same
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access permissions to files, belonging to user 10 in another
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namespace.
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The same is true for the IPC namespaces being shared - two users
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from different user namespaces should not access the same IPC objects
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even having equal UIDs.
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But currently this is not so.
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