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tty: Fix race in tty release

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Ian Abbott found that the tty layer would explode with the right set of
parallel open and close operations. This is because we race in the
handling of tty->drivers->termios[].

Correct this by
	Making tty_ldisc_release behave like nromal code (takes the lock,
			does stuff, drops the lock)
	Drop the tty lock earlier in tty_ldisc_release
	Taking the tty mutex around the driver->termios update in all cases
	Adding a WARN_ON to catch future screwups.

I also forgot to clean up the pty resources properly. With a pty pair we
need to pull both halves out of the tables.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Tested-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alan Cox
2012-07-27 18:02:54 +01:00
committed by Greg Kroah-Hartman
parent 373f5aedbc
commit d155255a34
3 changed files with 37 additions and 11 deletions
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3
drivers/tty/tty_ldisc.c
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@@ -912,7 +912,6 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
* race with the set_ldisc code path.
*/
tty_unlock();
tty_ldisc_halt(tty);
tty_ldisc_flush_works(tty);
tty_lock();
@@ -930,6 +929,8 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
tty_set_termios_ldisc(tty, N_TTY);
mutex_unlock(&tty->ldisc_mutex);
tty_unlock();
/* This will need doing differently if we need to lock */
if (o_tty)
tty_ldisc_release(o_tty, NULL);