// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*/
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#include <linux/types.h>
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#include <linux/errno.h>
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#include <linux/signal.h>
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#include <linux/sched/signal.h>
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#include <linux/sched/task.h>
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#include <linux/tty.h>
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#include <linux/fcntl.h>
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#include <linux/uaccess.h>
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#include "tty.h"
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static int is_ignored(int sig)
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{
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return (sigismember(¤t->blocked, sig) ||
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current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
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}
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/**
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* tty_check_change - check for POSIX terminal changes
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* @tty: tty to check
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*
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* If we try to write to, or set the state of, a terminal and we're
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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: ctrl_lock
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*/
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int __tty_check_change(struct tty_struct *tty, int sig)
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{
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unsigned long flags;
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struct pid *pgrp, *tty_pgrp;
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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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rcu_read_lock();
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pgrp = task_pgrp(current);
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spin_lock_irqsave(&tty->ctrl_lock, flags);
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tty_pgrp = tty->pgrp;
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spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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if (tty_pgrp && pgrp != tty_pgrp) {
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if (is_ignored(sig)) {
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if (sig == SIGTTIN)
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ret = -EIO;
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} else if (is_current_pgrp_orphaned())
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ret = -EIO;
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else {
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kill_pgrp(pgrp, sig, 1);
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set_thread_flag(TIF_SIGPENDING);
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ret = -ERESTARTSYS;
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}
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}
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rcu_read_unlock();
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if (!tty_pgrp)
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tty_warn(tty, "sig=%d, tty->pgrp == NULL!\n", sig);
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return ret;
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}
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int tty_check_change(struct tty_struct *tty)
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{
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return __tty_check_change(tty, SIGTTOU);
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}
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EXPORT_SYMBOL(tty_check_change);
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void proc_clear_tty(struct task_struct *p)
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{
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unsigned long flags;
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struct tty_struct *tty;
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spin_lock_irqsave(&p->sighand->siglock, flags);
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tty = p->signal->tty;
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p->signal->tty = NULL;
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spin_unlock_irqrestore(&p->sighand->siglock, flags);
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tty_kref_put(tty);
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}
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/**
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* proc_set_tty - set the controlling terminal
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*
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* Only callable by the session leader and only if it does not already have
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* a controlling terminal.
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*
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* Caller must hold: tty_lock()
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* a readlock on tasklist_lock
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* sighand lock
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*/
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static void __proc_set_tty(struct tty_struct *tty)
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{
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unsigned long flags;
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spin_lock_irqsave(&tty->ctrl_lock, flags);
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/*
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* The session and fg pgrp references will be non-NULL if
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* tiocsctty() is stealing the controlling tty
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*/
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put_pid(tty->session);
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put_pid(tty->pgrp);
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tty->pgrp = get_pid(task_pgrp(current));
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tty->session = get_pid(task_session(current));
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spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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if (current->signal->tty) {
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tty_debug(tty, "current tty %s not NULL!!\n",
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current->signal->tty->name);
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tty_kref_put(current->signal->tty);
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}
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put_pid(current->signal->tty_old_pgrp);
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current->signal->tty = tty_kref_get(tty);
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current->signal->tty_old_pgrp = NULL;
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}
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static void proc_set_tty(struct tty_struct *tty)
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{
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spin_lock_irq(¤t->sighand->siglock);
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__proc_set_tty(tty);
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spin_unlock_irq(¤t->sighand->siglock);
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}
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/*
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* Called by tty_open() to set the controlling tty if applicable.
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*/
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void tty_open_proc_set_tty(struct file *filp, struct tty_struct *tty)
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{
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read_lock(&tasklist_lock);
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spin_lock_irq(¤t->sighand->siglock);
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if (current->signal->leader &&
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!current->signal->tty &&
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tty->session == NULL) {
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/*
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* Don't let a process that only has write access to the tty
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* obtain the privileges associated with having a tty as
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* controlling terminal (being able to reopen it with full
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* access through /dev/tty, being able to perform pushback).
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* Many distributions set the group of all ttys to "tty" and
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* grant write-only access to all terminals for setgid tty
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* binaries, which should not imply full privileges on all ttys.
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*
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* This could theoretically break old code that performs open()
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* on a write-only file descriptor. In that case, it might be
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* necessary to also permit this if
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* inode_permission(inode, MAY_READ) == 0.
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*/
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if (filp->f_mode & FMODE_READ)
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__proc_set_tty(tty);
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}
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spin_unlock_irq(¤t->sighand->siglock);
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read_unlock(&tasklist_lock);
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}
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struct tty_struct *get_current_tty(void)
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{
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struct tty_struct *tty;
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unsigned long flags;
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spin_lock_irqsave(¤t->sighand->siglock, flags);
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tty = tty_kref_get(current->signal->tty);
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spin_unlock_irqrestore(¤t->sighand->siglock, flags);
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return tty;
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}
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EXPORT_SYMBOL_GPL(get_current_tty);
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/*
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* Called from tty_release().
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*/
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void session_clear_tty(struct pid *session)
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{
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struct task_struct *p;
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do_each_pid_task(session, PIDTYPE_SID, p) {
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proc_clear_tty(p);
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} while_each_pid_task(session, PIDTYPE_SID, p);
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}
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/**
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* tty_signal_session_leader - sends SIGHUP to session leader
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* @tty: controlling tty
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* @exit_session: if non-zero, signal all foreground group processes
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*
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* Send SIGHUP and SIGCONT to the session leader and its process group.
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* Optionally, signal all processes in the foreground process group.
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*
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* Returns the number of processes in the session with this tty
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* as their controlling terminal. This value is used to drop
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* tty references for those processes.
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*/
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int tty_signal_session_leader(struct tty_struct *tty, int exit_session)
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{
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struct task_struct *p;
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int refs = 0;
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struct pid *tty_pgrp = NULL;
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read_lock(&tasklist_lock);
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if (tty->session) {
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do_each_pid_task(tty->session, PIDTYPE_SID, p) {
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spin_lock_irq(&p->sighand->siglock);
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if (p->signal->tty == tty) {
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p->signal->tty = NULL;
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/* We defer the dereferences outside fo
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the tasklist lock */
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refs++;
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}
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if (!p->signal->leader) {
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spin_unlock_irq(&p->sighand->siglock);
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continue;
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}
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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(&tty->ctrl_lock);
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tty_pgrp = get_pid(tty->pgrp);
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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(&tty->ctrl_lock);
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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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if (tty_pgrp) {
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if (exit_session)
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kill_pgrp(tty_pgrp, SIGHUP, exit_session);
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put_pid(tty_pgrp);
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}
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return refs;
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}
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/**
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* disassociate_ctty - disconnect controlling tty
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* @on_exit: true if exiting so need to "hang up" the session
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*
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* This function is typically called only by the session leader, when
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* it wants to disassociate itself from its controlling tty.
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*
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* It performs the following functions:
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* (1) Sends a SIGHUP and SIGCONT to the foreground process group
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* (2) Clears the tty from being controlling the session
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* (3) Clears the controlling tty for all processes in the
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* session group.
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*
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* The argument on_exit is set to 1 if called when a process is
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* exiting; it is 0 if called by the ioctl TIOCNOTTY.
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*
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* Locking:
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* BTM is taken for hysterical raisons, and held when
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* called from no_tty().
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* tty_mutex is taken to protect tty
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* ->siglock is taken to protect ->signal/->sighand
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* tasklist_lock is taken to walk process list for sessions
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* ->siglock is taken to protect ->signal/->sighand
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*/
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void disassociate_ctty(int on_exit)
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{
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struct tty_struct *tty;
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if (!current->signal->leader)
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return;
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tty = get_current_tty();
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if (tty) {
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if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY) {
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tty_vhangup_session(tty);
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} else {
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struct pid *tty_pgrp = tty_get_pgrp(tty);
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if (tty_pgrp) {
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kill_pgrp(tty_pgrp, SIGHUP, on_exit);
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if (!on_exit)
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kill_pgrp(tty_pgrp, SIGCONT, on_exit);
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put_pid(tty_pgrp);
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}
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}
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tty_kref_put(tty);
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} else if (on_exit) {
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struct pid *old_pgrp;
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spin_lock_irq(¤t->sighand->siglock);
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old_pgrp = current->signal->tty_old_pgrp;
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current->signal->tty_old_pgrp = NULL;
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spin_unlock_irq(¤t->sighand->siglock);
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if (old_pgrp) {
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kill_pgrp(old_pgrp, SIGHUP, on_exit);
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kill_pgrp(old_pgrp, SIGCONT, on_exit);
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put_pid(old_pgrp);
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}
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return;
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}
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spin_lock_irq(¤t->sighand->siglock);
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put_pid(current->signal->tty_old_pgrp);
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current->signal->tty_old_pgrp = NULL;
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tty = tty_kref_get(current->signal->tty);
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spin_unlock_irq(¤t->sighand->siglock);
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if (tty) {
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unsigned long flags;
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tty_lock(tty);
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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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tty_unlock(tty);
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tty_kref_put(tty);
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}
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/* Now clear signal->tty under the lock */
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read_lock(&tasklist_lock);
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session_clear_tty(task_session(current));
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read_unlock(&tasklist_lock);
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}
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/*
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*
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* no_tty - Ensure the current process does not have a controlling tty
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*/
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void no_tty(void)
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{
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/* FIXME: Review locking here. The tty_lock never covered any race
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between a new association and proc_clear_tty but possible we need
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to protect against this anyway */
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struct task_struct *tsk = current;
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disassociate_ctty(0);
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proc_clear_tty(tsk);
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}
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/**
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* tiocsctty - set controlling tty
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* @tty: tty structure
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* @arg: user argument
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*
|
* This ioctl is used to manage job control. It permits a session
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* leader to set this tty as the controlling tty for the session.
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*
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* Locking:
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* Takes tty_lock() to serialize proc_set_tty() for this tty
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* Takes tasklist_lock internally to walk sessions
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* Takes ->siglock() when updating signal->tty
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*/
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static int tiocsctty(struct tty_struct *tty, struct file *file, int arg)
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{
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int ret = 0;
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tty_lock(tty);
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read_lock(&tasklist_lock);
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if (current->signal->leader && (task_session(current) == tty->session))
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goto unlock;
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/*
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* The process must be a session leader and
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* not have a controlling tty already.
|
*/
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if (!current->signal->leader || current->signal->tty) {
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ret = -EPERM;
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goto unlock;
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}
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if (tty->session) {
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/*
|
* This tty is already the controlling
|
* tty for another session group!
|
*/
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if (arg == 1 && capable(CAP_SYS_ADMIN)) {
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/*
|
* Steal it away
|
*/
|
session_clear_tty(tty->session);
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} else {
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ret = -EPERM;
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goto unlock;
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}
|
}
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|
/* See the comment in tty_open_proc_set_tty(). */
|
if ((file->f_mode & FMODE_READ) == 0 && !capable(CAP_SYS_ADMIN)) {
|
ret = -EPERM;
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goto unlock;
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}
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proc_set_tty(tty);
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unlock:
|
read_unlock(&tasklist_lock);
|
tty_unlock(tty);
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return ret;
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}
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/**
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* tty_get_pgrp - return a ref counted pgrp pid
|
* @tty: tty to read
|
*
|
* Returns a refcounted instance of the pid struct for the process
|
* group controlling the tty.
|
*/
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struct pid *tty_get_pgrp(struct tty_struct *tty)
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{
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unsigned long flags;
|
struct pid *pgrp;
|
|
spin_lock_irqsave(&tty->ctrl_lock, flags);
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pgrp = get_pid(tty->pgrp);
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spin_unlock_irqrestore(&tty->ctrl_lock, flags);
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|
return pgrp;
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}
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EXPORT_SYMBOL_GPL(tty_get_pgrp);
|
|
/*
|
* This checks not only the pgrp, but falls back on the pid if no
|
* satisfactory pgrp is found. I dunno - gdb doesn't work correctly
|
* without this...
|
*
|
* The caller must hold rcu lock or the tasklist lock.
|
*/
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static struct pid *session_of_pgrp(struct pid *pgrp)
|
{
|
struct task_struct *p;
|
struct pid *sid = NULL;
|
|
p = pid_task(pgrp, PIDTYPE_PGID);
|
if (p == NULL)
|
p = pid_task(pgrp, PIDTYPE_PID);
|
if (p != NULL)
|
sid = task_session(p);
|
|
return sid;
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}
|
|
/**
|
* tiocgpgrp - get process group
|
* @tty: tty passed by user
|
* @real_tty: tty side of the tty passed by the user if a pty else the tty
|
* @p: returned pid
|
*
|
* Obtain the process group of the tty. If there is no process group
|
* return an error.
|
*
|
* Locking: none. Reference to current->signal->tty is safe.
|
*/
|
static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
|
{
|
struct pid *pid;
|
int ret;
|
/*
|
* (tty == real_tty) is a cheap way of
|
* testing if the tty is NOT a master pty.
|
*/
|
if (tty == real_tty && current->signal->tty != real_tty)
|
return -ENOTTY;
|
pid = tty_get_pgrp(real_tty);
|
ret = put_user(pid_vnr(pid), p);
|
put_pid(pid);
|
return ret;
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}
|
|
/**
|
* tiocspgrp - attempt to set process group
|
* @tty: tty passed by user
|
* @real_tty: tty side device matching tty passed by user
|
* @p: pid pointer
|
*
|
* Set the process group of the tty to the session passed. Only
|
* permitted where the tty session is our session.
|
*
|
* Locking: RCU, ctrl lock
|
*/
|
static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
|
{
|
struct pid *pgrp;
|
pid_t pgrp_nr;
|
int retval = tty_check_change(real_tty);
|
|
if (retval == -EIO)
|
return -ENOTTY;
|
if (retval)
|
return retval;
|
|
if (get_user(pgrp_nr, p))
|
return -EFAULT;
|
if (pgrp_nr < 0)
|
return -EINVAL;
|
|
spin_lock_irq(&real_tty->ctrl_lock);
|
if (!current->signal->tty ||
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(current->signal->tty != real_tty) ||
|
(real_tty->session != task_session(current))) {
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retval = -ENOTTY;
|
goto out_unlock_ctrl;
|
}
|
rcu_read_lock();
|
pgrp = find_vpid(pgrp_nr);
|
retval = -ESRCH;
|
if (!pgrp)
|
goto out_unlock;
|
retval = -EPERM;
|
if (session_of_pgrp(pgrp) != task_session(current))
|
goto out_unlock;
|
retval = 0;
|
put_pid(real_tty->pgrp);
|
real_tty->pgrp = get_pid(pgrp);
|
out_unlock:
|
rcu_read_unlock();
|
out_unlock_ctrl:
|
spin_unlock_irq(&real_tty->ctrl_lock);
|
return retval;
|
}
|
|
/**
|
* tiocgsid - get session id
|
* @tty: tty passed by user
|
* @real_tty: tty side of the tty passed by the user if a pty else the tty
|
* @p: pointer to returned session id
|
*
|
* Obtain the session id of the tty. If there is no session
|
* return an error.
|
*/
|
static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
|
{
|
unsigned long flags;
|
pid_t sid;
|
|
/*
|
* (tty == real_tty) is a cheap way of
|
* testing if the tty is NOT a master pty.
|
*/
|
if (tty == real_tty && current->signal->tty != real_tty)
|
return -ENOTTY;
|
|
spin_lock_irqsave(&real_tty->ctrl_lock, flags);
|
if (!real_tty->session)
|
goto err;
|
sid = pid_vnr(real_tty->session);
|
spin_unlock_irqrestore(&real_tty->ctrl_lock, flags);
|
|
return put_user(sid, p);
|
|
err:
|
spin_unlock_irqrestore(&real_tty->ctrl_lock, flags);
|
return -ENOTTY;
|
}
|
|
/*
|
* Called from tty_ioctl(). If tty is a pty then real_tty is the slave side,
|
* if not then tty == real_tty.
|
*/
|
long tty_jobctrl_ioctl(struct tty_struct *tty, struct tty_struct *real_tty,
|
struct file *file, unsigned int cmd, unsigned long arg)
|
{
|
void __user *p = (void __user *)arg;
|
|
switch (cmd) {
|
case TIOCNOTTY:
|
if (current->signal->tty != tty)
|
return -ENOTTY;
|
no_tty();
|
return 0;
|
case TIOCSCTTY:
|
return tiocsctty(real_tty, file, arg);
|
case TIOCGPGRP:
|
return tiocgpgrp(tty, real_tty, p);
|
case TIOCSPGRP:
|
return tiocspgrp(tty, real_tty, p);
|
case TIOCGSID:
|
return tiocgsid(tty, real_tty, p);
|
}
|
return -ENOIOCTLCMD;
|
}
|
