forked from Minki/linux
redo locking of tty->pgrp
Historically tty->pgrp and friends were pid_t and the code "knew" they were safe. The change to pid structs opened up a few races and the removal of the BKL in places made them quite hittable. We put tty->pgrp under the ctrl_lock for the tty. Signed-off-by: Alan Cox <alan@redhat.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alan Cox
Linus Torvalds
parent
04f378b198
commit
47f86834bb
@ -1204,26 +1204,37 @@ EXPORT_SYMBOL_GPL(tty_find_polling_driver);
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* not in the foreground, send a SIGTTOU. If the signal is blocked or
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* ignored, go ahead and perform the operation. (POSIX 7.2)
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*
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* Locking: none - FIXME: review this
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* Locking: ctrl_lock - FIXME: review this
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*/
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int tty_check_change(struct tty_struct *tty)
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{
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unsigned long flags;
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int ret = 0;
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if (current->signal->tty != tty)
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return 0;
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spin_lock_irqsave(&tty->ctrl_lock, flags);
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if (!tty->pgrp) {
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printk(KERN_WARNING "tty_check_change: tty->pgrp == NULL!\n");
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return 0;
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goto out;
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}
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if (task_pgrp(current) == tty->pgrp)
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return 0;
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goto out;
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if (is_ignored(SIGTTOU))
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return 0;
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if (is_current_pgrp_orphaned())
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return -EIO;
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goto out;
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if (is_current_pgrp_orphaned()) {
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ret = -EIO;
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goto out;
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}
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kill_pgrp(task_pgrp(current), SIGTTOU, 1);
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set_thread_flag(TIF_SIGPENDING);
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return -ERESTARTSYS;
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ret = -ERESTARTSYS;
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out:
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spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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return ret;
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}
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EXPORT_SYMBOL(tty_check_change);
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@ -1403,6 +1414,7 @@ static void do_tty_hangup(struct work_struct *work)
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struct task_struct *p;
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struct tty_ldisc *ld;
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int closecount = 0, n;
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unsigned long flags;
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if (!tty)
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return;
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@ -1479,19 +1491,24 @@ static void do_tty_hangup(struct work_struct *work)
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__group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p);
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__group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p);
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put_pid(p->signal->tty_old_pgrp); /* A noop */
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spin_lock_irqsave(&tty->ctrl_lock, flags);
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if (tty->pgrp)
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p->signal->tty_old_pgrp = get_pid(tty->pgrp);
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spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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spin_unlock_irq(&p->sighand->siglock);
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} while_each_pid_task(tty->session, PIDTYPE_SID, p);
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}
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read_unlock(&tasklist_lock);
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spin_lock_irqsave(&tty->ctrl_lock, flags);
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tty->flags = 0;
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put_pid(tty->session);
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put_pid(tty->pgrp);
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tty->session = NULL;
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tty->pgrp = NULL;
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tty->ctrl_status = 0;
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spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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/*
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* If one of the devices matches a console pointer, we
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* cannot just call hangup() because that will cause
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@ -1666,10 +1683,13 @@ void disassociate_ctty(int on_exit)
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/* It is possible that do_tty_hangup has free'd this tty */
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tty = get_current_tty();
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if (tty) {
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unsigned long flags;
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spin_lock_irqsave(&tty->ctrl_lock, flags);
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put_pid(tty->session);
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put_pid(tty->pgrp);
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tty->session = NULL;
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tty->pgrp = NULL;
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spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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} else {
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#ifdef TTY_DEBUG_HANGUP
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printk(KERN_DEBUG "error attempted to write to tty [0x%p]"
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@ -1785,10 +1805,8 @@ EXPORT_SYMBOL(start_tty);
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* for hung up devices before calling the line discipline method.
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*
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* Locking:
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* Locks the line discipline internally while needed
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* For historical reasons the line discipline read method is
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* invoked under the BKL. This will go away in time so do not rely on it
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* in new code. Multiple read calls may be outstanding in parallel.
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* Locks the line discipline internally while needed. Multiple
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* read calls may be outstanding in parallel.
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*/
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static ssize_t tty_read(struct file *file, char __user *buf, size_t count,
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@ -2888,6 +2906,7 @@ static unsigned int tty_poll(struct file *filp, poll_table *wait)
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static int tty_fasync(int fd, struct file *filp, int on)
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{
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struct tty_struct *tty;
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unsigned long flags;
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int retval;
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tty = (struct tty_struct *)filp->private_data;
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@ -2903,6 +2922,7 @@ static int tty_fasync(int fd, struct file *filp, int on)
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struct pid *pid;
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if (!waitqueue_active(&tty->read_wait))
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tty->minimum_to_wake = 1;
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spin_lock_irqsave(&tty->ctrl_lock, flags);
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if (tty->pgrp) {
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pid = tty->pgrp;
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type = PIDTYPE_PGID;
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@ -2910,6 +2930,7 @@ static int tty_fasync(int fd, struct file *filp, int on)
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pid = task_pid(current);
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type = PIDTYPE_PID;
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}
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spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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retval = __f_setown(filp, pid, type, 0);
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if (retval)
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return retval;
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@ -2995,6 +3016,8 @@ static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
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struct winsize __user *arg)
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{
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struct winsize tmp_ws;
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struct pid *pgrp, *rpgrp;
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unsigned long flags;
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if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
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return -EFAULT;
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@ -3012,10 +3035,21 @@ static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
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}
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}
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#endif
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if (tty->pgrp)
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kill_pgrp(tty->pgrp, SIGWINCH, 1);
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if ((real_tty->pgrp != tty->pgrp) && real_tty->pgrp)
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kill_pgrp(real_tty->pgrp, SIGWINCH, 1);
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/* Get the PID values and reference them so we can
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avoid holding the tty ctrl lock while sending signals */
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spin_lock_irqsave(&tty->ctrl_lock, flags);
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pgrp = get_pid(tty->pgrp);
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rpgrp = get_pid(real_tty->pgrp);
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spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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if (pgrp)
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kill_pgrp(pgrp, SIGWINCH, 1);
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if (rpgrp != pgrp && rpgrp)
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kill_pgrp(rpgrp, SIGWINCH, 1);
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put_pid(pgrp);
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put_pid(rpgrp);
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tty->winsize = tmp_ws;
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real_tty->winsize = tmp_ws;
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done:
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@ -3171,7 +3205,7 @@ static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
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* Set the process group of the tty to the session passed. Only
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* permitted where the tty session is our session.
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*
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* Locking: RCU
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* Locking: RCU, ctrl lock
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*/
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static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
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@ -3179,6 +3213,7 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
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struct pid *pgrp;
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pid_t pgrp_nr;
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int retval = tty_check_change(real_tty);
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unsigned long flags;
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if (retval == -EIO)
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return -ENOTTY;
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@ -3201,8 +3236,10 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
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if (session_of_pgrp(pgrp) != task_session(current))
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goto out_unlock;
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retval = 0;
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spin_lock_irqsave(&tty->ctrl_lock, flags);
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put_pid(real_tty->pgrp);
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real_tty->pgrp = get_pid(pgrp);
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spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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out_unlock:
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rcu_read_unlock();
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return retval;
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@ -4077,14 +4114,19 @@ void proc_clear_tty(struct task_struct *p)
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}
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EXPORT_SYMBOL(proc_clear_tty);
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/* Called under the sighand lock */
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static void __proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
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{
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if (tty) {
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/* We should not have a session or pgrp to here but.... */
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unsigned long flags;
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/* We should not have a session or pgrp to put here but.... */
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spin_lock_irqsave(&tty->ctrl_lock, flags);
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put_pid(tty->session);
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put_pid(tty->pgrp);
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tty->session = get_pid(task_session(tsk));
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tty->pgrp = get_pid(task_pgrp(tsk));
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spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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tty->session = get_pid(task_session(tsk));
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}
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put_pid(tsk->signal->tty_old_pgrp);
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tsk->signal->tty = tty;
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@ -909,15 +909,21 @@ int vc_resize(struct vc_data *vc, unsigned int cols, unsigned int lines)
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if (vc->vc_tty) {
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struct winsize ws, *cws = &vc->vc_tty->winsize;
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unsigned long flags;
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memset(&ws, 0, sizeof(ws));
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ws.ws_row = vc->vc_rows;
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ws.ws_col = vc->vc_cols;
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ws.ws_ypixel = vc->vc_scan_lines;
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mutex_lock(&vc->vc_tty->termios_mutex);
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spin_lock_irqsave(&vc->vc_tty->ctrl_lock, flags);
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if ((ws.ws_row != cws->ws_row || ws.ws_col != cws->ws_col) &&
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vc->vc_tty->pgrp)
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kill_pgrp(vc->vc_tty->pgrp, SIGWINCH, 1);
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spin_unlock_irqrestore(&vc->vc_tty->ctrl_lock, flags);
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*cws = ws;
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mutex_unlock(&vc->vc_tty->termios_mutex);
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}
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if (CON_IS_VISIBLE(vc))
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@ -184,21 +184,22 @@ struct tty_struct {
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struct tty_ldisc ldisc;
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struct mutex termios_mutex;
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spinlock_t ctrl_lock;
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/* Termios values are protected by the termios mutex */
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struct ktermios *termios, *termios_locked;
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char name[64];
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struct pid *pgrp;
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struct pid *pgrp; /* Protected by ctrl lock */
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struct pid *session;
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unsigned long flags;
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int count;
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struct winsize winsize;
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struct winsize winsize; /* termios mutex */
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unsigned char stopped:1, hw_stopped:1, flow_stopped:1, packet:1;
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unsigned char low_latency:1, warned:1;
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unsigned char ctrl_status;
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unsigned char ctrl_status; /* ctrl_lock */
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unsigned int receive_room; /* Bytes free for queue */
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struct tty_struct *link;
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struct fasync_struct *fasync;
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struct tty_bufhead buf;
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struct tty_bufhead buf; /* Locked internally */
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int alt_speed; /* For magic substitution of 38400 bps */
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wait_queue_head_t write_wait;
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wait_queue_head_t read_wait;
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@ -212,6 +213,7 @@ struct tty_struct {
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/*
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* The following is data for the N_TTY line discipline. For
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* historical reasons, this is included in the tty structure.
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* Mostly locked by the BKL.
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*/
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unsigned int column;
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unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
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