linux-kernel - [PATCH 01/16] devpts: Use the same default mode for both /dev/ptmx and dev/pts/ptmx

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Message-Id: <1460734532-20134-1-git-send-email-ebiederm@xmission.com>
Date:	Fri, 15 Apr 2016 10:35:17 -0500
From:	"Eric W. Biederman" <ebiederm@...ssion.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>, security@...ian.org,
	security@...nel.org, Al Viro <viro@...iv.linux.org.uk>,
	security@...ntu.com, Peter Hurley <peter@...leysoftware.com>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	Willy Tarreau <w@....eu>,
	Aurelien Jarno <aurelien@...el32.net>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Jann Horn <jann@...jh.net>, Greg KH <greg@...ah.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jslaby@...e.com>,
	Florian Weimer <fw@...eb.enyo.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 01/16] devpts: Use the same default mode for both /dev/ptmx and dev/pts/ptmx

The default mode is 0666 on /dev/ptmx so we really don't gain anything
except a bunch of hassle by not having the default mode on
/dev/pts/ptmx also being 0666.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 drivers/tty/tty_io.c      | 5 +++--
 fs/devpts/inode.c         | 8 --------
 include/linux/devpts_fs.h | 3 +++
 3 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 8d26ed79bb4c..438b2209ea41 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3597,9 +3597,10 @@ static char *tty_devnode(struct device *dev, umode_t *mode)
 {
 	if (!mode)
 		return NULL;
-	if (dev->devt == MKDEV(TTYAUX_MAJOR, 0) ||
-	    dev->devt == MKDEV(TTYAUX_MAJOR, 2))
+	if (dev->devt == MKDEV(TTYAUX_MAJOR, 0))
 		*mode = 0666;
+	if (dev->devt == MKDEV(TTYAUX_MAJOR, PTMX_MINOR))
+		*mode = DEVPTS_DEFAULT_PTMX_MODE;
 	return NULL;
 }
 
diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index 655f21f99160..e8bf61cd1bf8 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -29,14 +29,6 @@
 #include <linux/seq_file.h>
 
 #define DEVPTS_DEFAULT_MODE 0600
-/*
- * ptmx is a new node in /dev/pts and will be unused in legacy (single-
- * instance) mode. To prevent surprises in user space, set permissions of
- * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
- * permissions.
- */
-#define DEVPTS_DEFAULT_PTMX_MODE 0000
-#define PTMX_MINOR	2
 
 /*
  * sysctl support for setting limits on the number of Unix98 ptys allocated.
diff --git a/include/linux/devpts_fs.h b/include/linux/devpts_fs.h
index e0ee0b3000b2..db329cd3d14e 100644
--- a/include/linux/devpts_fs.h
+++ b/include/linux/devpts_fs.h
@@ -15,6 +15,9 @@
 
 #include <linux/errno.h>
 
+#define DEVPTS_DEFAULT_PTMX_MODE 0666
+#define PTMX_MINOR	2
+
 #ifdef CONFIG_UNIX98_PTYS
 
 int devpts_new_index(struct inode *ptmx_inode);
-- 
2.8.1