linux-kernel - [PATCH] debugfs: more tightly restrict default mount mode

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Message-ID: <20120827203215.GA16637@www.outflux.net>
Date:	Mon, 27 Aug 2012 13:32:15 -0700
From:	Kees Cook <keescook@...omium.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ben Hutchings <ben@...adent.org.uk>,
	Rob Landley <rob@...dley.net>,
	Al Viro <viro@...iv.linux.org.uk>,
	Ludwig Nussel <ludwig.nussel@...e.de>,
	Alessandro Rubini <rubini@...dd.com>,
	Kees Cook <keescook@...omium.org>, linux-doc@...r.kernel.org
Subject: [PATCH] debugfs: more tightly restrict default mount mode

Since the debugfs is mostly only used by root, make the default mount
mode 0700. Most system owners do not need a more permissive value,
but they can choose to weaken the restrictions via their fstab.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 Documentation/filesystems/debugfs.txt |    4 ++--
 fs/debugfs/inode.c                    |    2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Documentation/filesystems/debugfs.txt b/Documentation/filesystems/debugfs.txt
index 7a34f82..3a863f6 100644
--- a/Documentation/filesystems/debugfs.txt
+++ b/Documentation/filesystems/debugfs.txt
@@ -15,8 +15,8 @@ Debugfs is typically mounted with a command like:
     mount -t debugfs none /sys/kernel/debug
 
 (Or an equivalent /etc/fstab line).
-The debugfs root directory is accessible by anyone by default. To
-restrict access to the tree the "uid", "gid" and "mode" mount
+The debugfs root directory is accessible only to the root user by
+default. To change access to the tree the "uid", "gid" and "mode" mount
 options can be used.
 
 Note that the debugfs API is exported GPL-only to modules.
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 4733eab..2d22c81 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -28,7 +28,7 @@
 #include <linux/magic.h>
 #include <linux/slab.h>
 
-#define DEBUGFS_DEFAULT_MODE	0755
+#define DEBUGFS_DEFAULT_MODE	0700
 
 static struct vfsmount *debugfs_mount;
 static int debugfs_mount_count;
-- 
1.7.0.4


-- 
Kees Cook
Chrome OS Security
--
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