diff options
| author | Peter Hurley <peter@hurleysoftware.com> | 2013-03-06 08:38:20 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-03-18 16:13:59 -0700 |
| commit | 01a5e440c91dc6065cf3dbc38aa7276fc4ce2f26 (patch) | |
| tree | 681cd21901b56dca6046fbc9516bb74221fa8b7a | |
| parent | 8c985d18b136c5d511445d15f0c6650003a8946b (diff) | |
n_tty: Lock access to tty->pgrp for POSIX job control
Concurrent access to tty->pgrp must be protected with tty->ctrl_lock.
Also, as noted in the comments, reading current->signal->tty is
safe because either,
1) current->signal->tty is assigned by current, or
2) current->signal->tty is set to NULL.
NB: for reference, tty_check_change() implements a similar POSIX
check for the ioctls corresponding to tcflush(), tcdrain(),
tcsetattr(), tcsetpgrp(), tcflow() and tcsendbreak().
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/n_tty.c | 34 |
1 files changed, 18 insertions, 16 deletions
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 61f1bc97ccd9..68865d9af8a0 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -1719,10 +1719,9 @@ extern ssize_t redirected_tty_write(struct file *, const char __user *, * and if appropriate send any needed signals and return a negative * error code if action should be taken. * - * FIXME: - * Locking: None - redirected write test is safe, testing - * current->signal should possibly lock current->sighand - * pgrp locking ? + * Locking: redirected write test is safe + * current->signal->tty check is safe + * ctrl_lock to safely reference tty->pgrp */ static int job_control(struct tty_struct *tty, struct file *file) @@ -1732,19 +1731,22 @@ static int job_control(struct tty_struct *tty, struct file *file) /* NOTE: not yet done after every sleep pending a thorough check of the logic of this change. -- jlc */ /* don't stop on /dev/console */ - if (file->f_op->write != redirected_tty_write && - current->signal->tty == tty) { - if (!tty->pgrp) - printk(KERN_ERR "n_tty_read: no tty->pgrp!\n"); - else if (task_pgrp(current) != tty->pgrp) { - if (is_ignored(SIGTTIN) || - is_current_pgrp_orphaned()) - return -EIO; - kill_pgrp(task_pgrp(current), SIGTTIN, 1); - set_thread_flag(TIF_SIGPENDING); - return -ERESTARTSYS; - } + if (file->f_op->write == redirected_tty_write || + current->signal->tty != tty) + return 0; + + spin_lock_irq(&tty->ctrl_lock); + if (!tty->pgrp) + printk(KERN_ERR "n_tty_read: no tty->pgrp!\n"); + else if (task_pgrp(current) != tty->pgrp) { + spin_unlock_irq(&tty->ctrl_lock); + if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned()) + return -EIO; + kill_pgrp(task_pgrp(current), SIGTTIN, 1); + set_thread_flag(TIF_SIGPENDING); + return -ERESTARTSYS; } + spin_unlock_irq(&tty->ctrl_lock); return 0; } |