[RESEND PATCH v6 1/5] docs: proc: add documentation about mount restrictions

Alexey Gladkov
2021-07-16T10:46:49Z

Signed-off-by: Alexey Gladkov <legion@kernel.org>
---
Documentation/filesystems/proc.rst | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 2fa69f710e2a..5a1bb0e081fd 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -50,6 +50,7 @@ fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009

4 Configuring procfs
4.1 Mount options
+ 4.2 Mount restrictions

5 Filesystem behavior

@@ -2175,6 +2176,19 @@ information about processes information, just add identd to this group.
subset=pid hides all top level files and directories in the procfs that
are not related to tasks.

+4.2 Mount restrictions
+--------------------------
+
+If user namespaces are in use, the kernel additionally checks the instances of
+procfs available to the mounter and will not allow procfs to be mounted if:
+
+ 1. This mount is not fully visible.
+
+ a. It's root directory is not the root directory of the filesystem.
+ b. If any file or non-empty procfs directory is hidden by another mount.
+
+ 2. A new mount overrides the readonly option or any option from atime familty.
+
Chapter 5: Filesystem behavior
==============================

--
2.29.3