Commit 55199ea3 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman

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

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: default avatarAlan Cox <alan@linux.intel.com>
Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 216030ec
......@@ -383,6 +383,10 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
int idx = tty->index;
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[1] = kmalloc(sizeof **ports, GFP_KERNEL);
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.
*/
tty_driver_kref_get(driver->other);
if (driver->subtype == PTY_TYPE_MASTER)
o_tty->count++;
/* Establish the links in both directions */
tty->link = o_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->count++;
o_tty->count++;
return 0;
err_free_termios:
if (legacy)
......
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