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pty: Always return -EIO if slave BSD pty opened first

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Opening the slave BSD pty first already returns -EIO from the slave
pty_open(), which in turn causes the newly installed tty pair to be
released before returning from tty_open(). However, this can also
cause a parallel master BSD pty open to fail because the pty pair
destruction may already been taking place in tty_release().

Failing at driver->install() if the slave pty is opened first ensures
that a pty master open cannot fail, because the driver tables will
not have been updated so tty_driver_lookup_tty() won't find the
master pty (and attempt to "re-open" it).

In turn, this guarantees that any tty with a tty->count == 0 is
in final close (rather than never opened).

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2014-11-05 12:12:49 -05:00 committed by Greg Kroah-Hartman
parent 216030ec55
commit 55199ea3bd
1 changed files with 5 additions and 2 deletions
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7
drivers/tty/pty.c
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@ -383,6 +383,10 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
int idx = tty->index; int idx = tty->index;
int retval = -ENOMEM; int retval = -ENOMEM;
/* Opening the slave first has always returned -EIO */
if (driver->subtype != PTY_TYPE_MASTER)
return -EIO;
ports[0] = kmalloc(sizeof **ports, GFP_KERNEL); ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
ports[1] = kmalloc(sizeof **ports, GFP_KERNEL); ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
if (!ports[0] || !ports[1]) if (!ports[0] || !ports[1])
@ -419,8 +423,6 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
* Everything allocated ... set up the o_tty structure. * Everything allocated ... set up the o_tty structure.
*/ */
tty_driver_kref_get(driver->other); tty_driver_kref_get(driver->other);
if (driver->subtype == PTY_TYPE_MASTER)
o_tty->count++;
/* Establish the links in both directions */ /* Establish the links in both directions */
tty->link = o_tty; tty->link = o_tty;
o_tty->link = tty; o_tty->link = tty;
@ -432,6 +434,7 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
tty_driver_kref_get(driver); tty_driver_kref_get(driver);
tty->count++; tty->count++;
o_tty->count++;
return 0; return 0;
err_free_termios: err_free_termios:
if (legacy) if (legacy)