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[PATCH] tty: hide unused pty_get_peer function

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  [PATCH] tty: hide unused pty_get_peer function Arnd Bergmann <arnd@arndb.de> - 2017-06-20 22:40 +0200
    Re: [PATCH] tty: hide unused pty_get_peer function Kees Cook <keescook@chromium.org> - 2017-06-21 00:40 +0200
    Re: [PATCH] tty: hide unused pty_get_peer function Aleksa Sarai <asarai@suse.de> - 2017-06-21 01:20 +0200

#1671090 — [PATCH] tty: hide unused pty_get_peer function

TIOCGPTPEER is only used for unix98 PTYs, and we get a warning
when those are disabled:

drivers/tty/pty.c:466:12: error: 'pty_get_peer' defined but not used [-Werror=unused-function]

This moves the respective functions inside of the existing #ifdef.

Fixes: 54ebbfb16034 ("tty: add TIOCGPTPEER ioctl")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/tty/pty.c | 85 +++++++++++++++++++++++++++----------------------------
 1 file changed, 42 insertions(+), 43 deletions(-)

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index d1399aac05a1..284749fb0f6b 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -448,48 +448,6 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
 	return retval;
 }
 
-/**
- *	pty_open_peer - open the peer of a pty
- *	@tty: the peer of the pty being opened
- *
- *	Open the cached dentry in tty->link, providing a safe way for userspace
- *	to get the slave end of a pty (where they have the master fd and cannot
- *	access or trust the mount namespace /dev/pts was mounted inside).
- */
-static struct file *pty_open_peer(struct tty_struct *tty, int flags)
-{
-	if (tty->driver->subtype != PTY_TYPE_MASTER)
-		return ERR_PTR(-EIO);
-	return dentry_open(tty->link->driver_data, flags, current_cred());
-}
-
-static int pty_get_peer(struct tty_struct *tty, int flags)
-{
-	int fd = -1;
-	struct file *filp = NULL;
-	int retval = -EINVAL;
-
-	fd = get_unused_fd_flags(0);
-	if (fd < 0) {
-		retval = fd;
-		goto err;
-	}
-
-	filp = pty_open_peer(tty, flags);
-	if (IS_ERR(filp)) {
-		retval = PTR_ERR(filp);
-		goto err_put;
-	}
-
-	fd_install(fd, filp);
-	return fd;
-
-err_put:
-	put_unused_fd(fd);
-err:
-	return retval;
-}
-
 static void pty_cleanup(struct tty_struct *tty)
 {
 	tty_port_put(tty->port);
@@ -646,9 +604,50 @@ static inline void legacy_pty_init(void) { }
 
 /* Unix98 devices */
 #ifdef CONFIG_UNIX98_PTYS
-
 static struct cdev ptmx_cdev;
 
+/**
+ *	pty_open_peer - open the peer of a pty
+ *	@tty: the peer of the pty being opened
+ *
+ *	Open the cached dentry in tty->link, providing a safe way for userspace
+ *	to get the slave end of a pty (where they have the master fd and cannot
+ *	access or trust the mount namespace /dev/pts was mounted inside).
+ */
+static struct file *pty_open_peer(struct tty_struct *tty, int flags)
+{
+	if (tty->driver->subtype != PTY_TYPE_MASTER)
+		return ERR_PTR(-EIO);
+	return dentry_open(tty->link->driver_data, flags, current_cred());
+}
+
+static int pty_get_peer(struct tty_struct *tty, int flags)
+{
+	int fd = -1;
+	struct file *filp = NULL;
+	int retval = -EINVAL;
+
+	fd = get_unused_fd_flags(0);
+	if (fd < 0) {
+		retval = fd;
+		goto err;
+	}
+
+	filp = pty_open_peer(tty, flags);
+	if (IS_ERR(filp)) {
+		retval = PTR_ERR(filp);
+		goto err_put;
+	}
+
+	fd_install(fd, filp);
+	return fd;
+
+err_put:
+	put_unused_fd(fd);
+err:
+	return retval;
+}
+
 static int pty_unix98_ioctl(struct tty_struct *tty,
 			    unsigned int cmd, unsigned long arg)
 {
-- 
2.9.0

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#1671200

On Tue, Jun 20, 2017 at 1:34 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> TIOCGPTPEER is only used for unix98 PTYs, and we get a warning
> when those are disabled:
>
> drivers/tty/pty.c:466:12: error: 'pty_get_peer' defined but not used [-Werror=unused-function]
>
> This moves the respective functions inside of the existing #ifdef.
>
> Fixes: 54ebbfb16034 ("tty: add TIOCGPTPEER ioctl")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

-- 
Kees Cook
Pixel Security

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#1671229

> TIOCGPTPEER is only used for unix98 PTYs, and we get a warning
> when those are disabled:
> 
> drivers/tty/pty.c:466:12: error: 'pty_get_peer' defined but not used [-Werror=unused-function]
> 
> This moves the respective functions inside of the existing #ifdef.
> 
> Fixes: 54ebbfb16034 ("tty: add TIOCGPTPEER ioctl")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Oops, I missed that.

   Acked-by: Aleksa Sarai <asarai@suse.de>

-- 
Aleksa Sarai
Software Engineer (Containers)
SUSE Linux GmbH
https://www.cyphar.com/

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