diff options
| author | Peter Hurley <peter@hurleysoftware.com> | 2016-01-09 21:45:11 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-01-28 11:58:02 -0800 |
| commit | a8f3a29718f77df3116955d100756f67fafabec0 (patch) | |
| tree | 435e824fef69ff9d08e6df6baf06fde5a31c2b5e /drivers | |
| parent | f557474ca3a23800dffb790846bcb121fa046c71 (diff) | |
tty: Fix ioctl(FIOASYNC) on hungup file
A small race window exists which allows signal-driven async i/o to be
enabled for the tty when the file ptr has already been hungup and
signal-driven i/o has been disabled:
CPU 0 CPU 1
----- ------
ioctl_fioasync(on)
filp->f_op->fasync(on) __tty_hangup()
tty_fasync(on) tty_lock()
tty_lock() ...
. filp->f_op = &hung_up_tty_fops;
(waiting) __tty_fasync(off)
. tty_unlock()
/* gets tty lock */
/* enables FASYNC */
Check the tty has not been hungup while holding tty_lock.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/tty/tty_io.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 0140c8669ada..8d26ed79bb4c 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -2260,10 +2260,11 @@ out: static int tty_fasync(int fd, struct file *filp, int on) { struct tty_struct *tty = file_tty(filp); - int retval; + int retval = -ENOTTY; tty_lock(tty); - retval = __tty_fasync(fd, filp, on); + if (!tty_hung_up_p(filp)) + retval = __tty_fasync(fd, filp, on); tty_unlock(tty); return retval; |