From: Alexey Gladkov <gladkov.alexey@gmail.com>
To: LKML <linux-kernel@vger.kernel.org>,
"Eric W . Biederman" <ebiederm@xmission.com>
Cc: Linux FS Devel <linux-fsdevel@vger.kernel.org>,
Linux Containers <containers@lists.linux-foundation.org>,
Alexey Gladkov <legion@kernel.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Kees Cook <keescook@chromium.org>
Subject: [PATCH v5 1/5] docs: proc: add documentation about mount restrictions
Date: Wed, 10 Mar 2021 19:19:56 +0100 [thread overview]
Message-ID: <333cf0c988255d7bf54871ad4fa02af2aaa8d4a3.1615400395.git.gladkov.alexey@gmail.com> (raw)
In-Reply-To: <cover.1615400395.git.gladkov.alexey@gmail.com>
Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
---
Documentation/filesystems/proc.rst | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 2fa69f710e2a..3daf0e7d1071 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 +2176,21 @@ 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
+--------------------------
+
+The procfs can be mounted without any special restrictions if user namespace is
+not used. You only need to have permission to mount (CAP_SYS_ADMIN).
+
+If you are inside the user namespace, the kernel checks the instances of procfs
+available to you and will not allow procfs to be mounted if:
+
+ 1. There is a bind mount of part of procfs visible. Whoever mounts should be
+ able to see the entire filesystem.
+ 2. Mount is prohibited if a new mount overrides the readonly option or family
+ of atime options.
+ 3. If any file or non-empty procfs directory is hidden by another filesystem.
+
Chapter 5: Filesystem behavior
==============================
--
2.29.2
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next prev parent reply other threads:[~2021-03-10 18:20 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-10 18:19 [PATCH v5 0/5] proc: Relax check of mount visibility Alexey Gladkov
2021-03-10 18:19 ` Alexey Gladkov [this message]
2021-03-10 18:19 ` [PATCH v5 2/5] proc: Show /proc/self/net only for CAP_NET_ADMIN Alexey Gladkov
2021-03-10 18:19 ` [PATCH v5 3/5] proc: Disable cancellation of subset=pid option Alexey Gladkov
2021-03-10 18:19 ` [PATCH v5 4/5] proc: Relax check of mount visibility Alexey Gladkov
2021-03-10 19:42 ` kernel test robot
2021-03-10 18:20 ` [PATCH v5 5/5] docs: proc: add documentation about relaxing visibility restrictions Alexey Gladkov
2021-03-10 20:07 ` [PATCH v5 0/5] proc: Relax check of mount visibility Alexey Gladkov
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