tty: cleanup prohibition of direct opening for unix98 pty master

cleanup hack added in v2.6.27-3203-g15582d3

comment from that patch:

: pty: If the administrator creates a device for a ptmx slave we should not error
:
: The open path for ptmx slaves is via the ptmx device. Opening them any
: other way is not allowed. Vegard Nossum found that previously this was not
: the case and mknod foo c 128 42; cat foo would produce nasty diagnostics
:
: Signed-off-by: Alan Cox <alan@redhat.com>
: Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

devpts_get_tty() returns non-null only for inodes on devpts, but there is no
inodes for master-devices, /dev/ptmx (/dev/pts/ptmx) is the only way to open them.
Thus we can completely forbid lookup for master-devices and eliminate that hack in
tty_init_dev() because tty_open() will get EIO from tty_driver_lookup_tty().

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 10 deletions

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index e41b9bbc107d..fbcc14063804 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1365,7 +1365,6 @@ static int tty_reopen(struct tty_struct *tty)
  *      @driver: tty driver we are opening a device on
  *      @idx: device index
  *      @ret_tty: returned tty structure
- *      @first_ok: ok to open a new device (used by ptmx)
  *
  *      Prepare a tty device. This may not be a "new" clean device but
  *      could also be an active device. The pty drivers require special
@@ -1385,18 +1384,11 @@ static int tty_reopen(struct tty_struct *tty)
  * relaxed for the (most common) case of reopening a tty.
  */
 
-struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
-                                                                int first_ok)
+struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
 {
         struct tty_struct *tty;
         int retval;
 
-        /* Check if pty master is being opened multiple times */
-        if (driver->subtype == PTY_TYPE_MASTER &&
-                (driver->flags & TTY_DRIVER_DEVPTS_MEM) && !first_ok) {
-                return ERR_PTR(-EIO);
-        }
-
         /*
          * First time open is complex, especially for PTY devices.
          * This code guarantees that either everything succeeds and the
@@ -1950,7 +1942,7 @@ retry_open:
                 if (retval)
                         tty = ERR_PTR(retval);
         } else
-                tty = tty_init_dev(driver, index, 0);
+                tty = tty_init_dev(driver, index);
 
         mutex_unlock(&tty_mutex);
         if (driver)