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| author | Rosen Penev <rosenp@gmail.com> | 2026-09-27 13:35:01 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-10-01 11:04:53 +0200 |
| commit | 8167c1f071426706c233e93ecfd13aba7d5c06c8 (patch) | |
| tree | 2c0cd5f5e1cc35eadee98d49fe034f96a88856ce /Documentation/admin-guide/namespaces | |
| download | linux-stable-8167c1f071426706c233e93ecfd13aba7d5c06c8.tar.gz linux-stable-8167c1f071426706c233e93ecfd13aba7d5c06c8.zip | |
tty: serial: mpc52xx_uart: move static declarations up.grafted
Avoid a compilation error so that they're not used before being
declared.
Fixes: 4d105880666a ("tty: serial: mpc52xx_uart: add bounds check for psc_num array index")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202609260356.tJWbd1WU-lkp@intel.com/
Signed-off-by: Rosen Penev <rosenp@gmail.com>
Link: https://patch.msgid.link/20260927203501.14105-1-rosenp@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/admin-guide/namespaces')
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 new file mode 100644 index 000000000..318800b2a --- /dev/null +++ b/Documentation/admin-guide/namespaces/compatibility-list.rst @@ -0,0 +1,43 @@ +============================= +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 new file mode 100644 index 000000000..384f2e0f3 --- /dev/null +++ b/Documentation/admin-guide/namespaces/index.rst @@ -0,0 +1,11 @@ +.. 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 new file mode 100644 index 000000000..553a44803 --- /dev/null +++ b/Documentation/admin-guide/namespaces/resource-control.rst @@ -0,0 +1,18 @@ +==================================== +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. |
