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authorRob Herring (Arm) <robh@kernel.org>2026-08-31 14:43:51 -0500
committerDmitry Torokhov <dmitry.torokhov@gmail.com>2026-09-13 18:17:31 -0700
commit55fc280e951ab2b39f3dcb640edc1b1eebc6d173 (patch)
treef0b5f37b42fc13b9908a31b657c646b024231cdd /Documentation/admin-guide/namespaces
downloadlinux-stable-55fc280e951ab2b39f3dcb640edc1b1eebc6d173.tar.gz
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Input: tsc2007 - read "ti,poll-period" as u32grafted
The "ti,poll-period" property is documented as a normal uint32 cell. The driver used a u64 helper, which makes the helper type disagree with the schema even though the stored value is still small. Read "ti,poll-period" with the u32 helper matching the documented DT cell size. Assisted-by: Codex:gpt-5-5 Signed-off-by: Rob Herring (Arm) <robh@kernel.org> Link: https://patch.msgid.link/20260831194352.1185860-1-robh@kernel.org Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Diffstat (limited to 'Documentation/admin-guide/namespaces')
-rw-r--r--Documentation/admin-guide/namespaces/compatibility-list.rst43
-rw-r--r--Documentation/admin-guide/namespaces/index.rst11
-rw-r--r--Documentation/admin-guide/namespaces/resource-control.rst18
3 files changed, 72 insertions, 0 deletions
diff --git a/Documentation/admin-guide/namespaces/compatibility-list.rst b/Documentation/admin-guide/namespaces/compatibility-list.rst
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+=============================
+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.
diff --git a/Documentation/admin-guide/namespaces/index.rst b/Documentation/admin-guide/namespaces/index.rst
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+.. SPDX-License-Identifier: GPL-2.0
+
+==========
+Namespaces
+==========
+
+.. toctree::
+ :maxdepth: 1
+
+ compatibility-list
+ resource-control
diff --git a/Documentation/admin-guide/namespaces/resource-control.rst b/Documentation/admin-guide/namespaces/resource-control.rst
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+====================================
+User namespaces and resource control
+====================================
+
+The kernel contains many kinds of objects that either don't have
+individual limits or that have limits which are ineffective when
+a set of processes is allowed to switch their UID. On a system
+where the admins don't trust their users or their users' programs,
+user namespaces expose the system to potential misuse of resources.
+
+In order to mitigate this, we recommend that admins enable memory
+control groups on any system that enables user namespaces.
+Furthermore, we recommend that admins configure the memory control
+groups to limit the maximum memory usable by any untrusted user.
+
+Memory control groups can be configured by installing the libcgroup
+package present on most distros editing /etc/cgrules.conf,
+/etc/cgconfig.conf and setting up libpam-cgroup.