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tty: Retry failed reopen if tty teardown in-progress

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commit 7f22f6c935cda600660e623a411fe380015d28d9 upstream.

A small window exists where a tty reopen will observe the tty
just prior to imminent teardown (tty->count == 0); in this case, open()
returns EIO to userspace.

Instead, retry the open after checking for signals and yielding;
this interruptible retry loop allows teardown to commence and initialize
a new tty on retry. Never retry the BSD master pty reopen; there is no
guarantee the pty pair teardown is imminent since the slave file
descriptors may remain open indefinitely.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley
2016-01-09 21:13:45 -08:00
committed by Greg Kroah-Hartman
parent c35f123493
commit b431225014
1 changed files with 8 additions and 4 deletions
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12
drivers/tty/tty_io.c
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@@ -1462,13 +1462,13 @@ static int tty_reopen(struct tty_struct *tty)
{
struct tty_driver *driver = tty->driver;
if (!tty->count)
return -EIO;
if (driver->type == TTY_DRIVER_TYPE_PTY &&
driver->subtype == PTY_TYPE_MASTER)
return -EIO;
if (!tty->count)
return -EAGAIN;
if (test_bit(TTY_EXCLUSIVE, &tty->flags) && !capable(CAP_SYS_ADMIN))
return -EBUSY;
@@ -2092,7 +2092,11 @@ retry_open:
if (IS_ERR(tty)) {
retval = PTR_ERR(tty);
goto err_file;
if (retval != -EAGAIN || signal_pending(current))
goto err_file;
tty_free_file(filp);
schedule();
goto retry_open;
}
tty_add_file(tty, filp);