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Message-Id: <e57f67df145fd79baabd4c8cbaa75c7d1269282a.1615567183.git.gladkov.alexey@gmail.com>
Date: Fri, 12 Mar 2021 17:41:44 +0100
From: Alexey Gladkov <gladkov.alexey@...il.com>
To: LKML <linux-kernel@...r.kernel.org>,
"Eric W . Biederman" <ebiederm@...ssion.com>
Cc: Alexey Gladkov <legion@...nel.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Kees Cook <keescook@...omium.org>,
Linux Containers <containers@...ts.linux-foundation.org>,
Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: [PATCH v6 1/5] docs: proc: add documentation about mount restrictions
Signed-off-by: Alexey Gladkov <gladkov.alexey@...il.com>
---
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@...bold.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
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