linux-kernel - [PATCH 2/4] devpts: Set the default permissions of /dev/pts/ptmx and /dev/ptmx to 0666

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Message-ID: <87ipb5760e.fsf_-_@xmission.com>
Date:	Sat, 22 Sep 2012 20:49:37 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Kay Sievers <kay.sievers@...y.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	containers@...ts.linux-foundation.org,
	Dave Hansen <haveblue@...ibm.com>,
	linux-kernel@...r.kernel.org, Andy Whitcroft <apw@...onical.com>,
	sukadev@...ux.vnet.ibm.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Serge Hallyn <serge.hallyn@...onical.com>
Subject: [PATCH 2/4] devpts: Set the default permissions of /dev/pts/ptmx and /dev/ptmx to 0666


These are difference instances of the same device not so it only
makes sense that they would have the same default permissions.

Move the definitions of DEVPTS_DEEFAULT_PTMX_MODE and PTM_MINOR
into devpts_fs.h so we can use the same definitions throughout.

Acked-by: "Serge E. Hallyn" <serge@...lyn.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 drivers/tty/pty.c         |    6 +++---
 drivers/tty/tty_io.c      |    5 +++--
 fs/devpts/inode.c         |    8 --------
 include/linux/devpts_fs.h |    3 +++
 4 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 5505ffc..6beb7e1 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -722,10 +722,10 @@ static void __init unix98_pty_init(void)
 	ptmx_fops.open = ptmx_open;
 
 	cdev_init(&ptmx_cdev, &ptmx_fops);
-	if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
-	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
+	if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, PTMX_MINOR), 1) ||
+	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, PTMX_MINOR), 1, "/dev/ptmx") < 0)
 		panic("Couldn't register /dev/ptmx driver\n");
-	device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
+	device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, PTMX_MINOR), NULL, "ptmx");
 }
 
 #else
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index b425c79..6c3a7c2 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3314,9 +3314,10 @@ 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 5f0d64e..61b54aa 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -27,14 +27,6 @@
 #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 5ce0e5f..2d539ae 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);
-- 
1.7.5.4

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