2 * Copyright (C) 1991, 1992 Linus Torvalds
5 #include <linux/types.h>
6 #include <linux/errno.h>
7 #include <linux/signal.h>
8 #include <linux/sched/signal.h>
9 #include <linux/sched/task.h>
10 #include <linux/tty.h>
11 #include <linux/fcntl.h>
12 #include <linux/uaccess.h>
14 static int is_ignored(int sig)
16 return (sigismember(¤t->blocked, sig) ||
17 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
21 * tty_check_change - check for POSIX terminal changes
24 * If we try to write to, or set the state of, a terminal and we're
25 * not in the foreground, send a SIGTTOU. If the signal is blocked or
26 * ignored, go ahead and perform the operation. (POSIX 7.2)
30 int __tty_check_change(struct tty_struct *tty, int sig)
33 struct pid *pgrp, *tty_pgrp;
36 if (current->signal->tty != tty)
40 pgrp = task_pgrp(current);
42 spin_lock_irqsave(&tty->ctrl_lock, flags);
44 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
46 if (tty_pgrp && pgrp != tty->pgrp) {
47 if (is_ignored(sig)) {
50 } else if (is_current_pgrp_orphaned())
53 kill_pgrp(pgrp, sig, 1);
54 set_thread_flag(TIF_SIGPENDING);
61 tty_warn(tty, "sig=%d, tty->pgrp == NULL!\n", sig);
66 int tty_check_change(struct tty_struct *tty)
68 return __tty_check_change(tty, SIGTTOU);
70 EXPORT_SYMBOL(tty_check_change);
72 void proc_clear_tty(struct task_struct *p)
75 struct tty_struct *tty;
76 spin_lock_irqsave(&p->sighand->siglock, flags);
78 p->signal->tty = NULL;
79 spin_unlock_irqrestore(&p->sighand->siglock, flags);
84 * proc_set_tty - set the controlling terminal
86 * Only callable by the session leader and only if it does not already have
87 * a controlling terminal.
89 * Caller must hold: tty_lock()
90 * a readlock on tasklist_lock
93 static void __proc_set_tty(struct tty_struct *tty)
97 spin_lock_irqsave(&tty->ctrl_lock, flags);
99 * The session and fg pgrp references will be non-NULL if
100 * tiocsctty() is stealing the controlling tty
102 put_pid(tty->session);
104 tty->pgrp = get_pid(task_pgrp(current));
105 tty->session = get_pid(task_session(current));
106 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
107 if (current->signal->tty) {
108 tty_debug(tty, "current tty %s not NULL!!\n",
109 current->signal->tty->name);
110 tty_kref_put(current->signal->tty);
112 put_pid(current->signal->tty_old_pgrp);
113 current->signal->tty = tty_kref_get(tty);
114 current->signal->tty_old_pgrp = NULL;
117 static void proc_set_tty(struct tty_struct *tty)
119 spin_lock_irq(¤t->sighand->siglock);
121 spin_unlock_irq(¤t->sighand->siglock);
125 * Called by tty_open() to set the controlling tty if applicable.
127 void tty_open_proc_set_tty(struct file *filp, struct tty_struct *tty)
129 read_lock(&tasklist_lock);
130 spin_lock_irq(¤t->sighand->siglock);
131 if (current->signal->leader &&
132 !current->signal->tty &&
133 tty->session == NULL) {
135 * Don't let a process that only has write access to the tty
136 * obtain the privileges associated with having a tty as
137 * controlling terminal (being able to reopen it with full
138 * access through /dev/tty, being able to perform pushback).
139 * Many distributions set the group of all ttys to "tty" and
140 * grant write-only access to all terminals for setgid tty
141 * binaries, which should not imply full privileges on all ttys.
143 * This could theoretically break old code that performs open()
144 * on a write-only file descriptor. In that case, it might be
145 * necessary to also permit this if
146 * inode_permission(inode, MAY_READ) == 0.
148 if (filp->f_mode & FMODE_READ)
151 spin_unlock_irq(¤t->sighand->siglock);
152 read_unlock(&tasklist_lock);
155 struct tty_struct *get_current_tty(void)
157 struct tty_struct *tty;
160 spin_lock_irqsave(¤t->sighand->siglock, flags);
161 tty = tty_kref_get(current->signal->tty);
162 spin_unlock_irqrestore(¤t->sighand->siglock, flags);
165 EXPORT_SYMBOL_GPL(get_current_tty);
168 * Called from tty_release().
170 void session_clear_tty(struct pid *session)
172 struct task_struct *p;
173 do_each_pid_task(session, PIDTYPE_SID, p) {
175 } while_each_pid_task(session, PIDTYPE_SID, p);
179 * tty_signal_session_leader - sends SIGHUP to session leader
180 * @tty controlling tty
181 * @exit_session if non-zero, signal all foreground group processes
183 * Send SIGHUP and SIGCONT to the session leader and its process group.
184 * Optionally, signal all processes in the foreground process group.
186 * Returns the number of processes in the session with this tty
187 * as their controlling terminal. This value is used to drop
188 * tty references for those processes.
190 int tty_signal_session_leader(struct tty_struct *tty, int exit_session)
192 struct task_struct *p;
194 struct pid *tty_pgrp = NULL;
196 read_lock(&tasklist_lock);
198 do_each_pid_task(tty->session, PIDTYPE_SID, p) {
199 spin_lock_irq(&p->sighand->siglock);
200 if (p->signal->tty == tty) {
201 p->signal->tty = NULL;
202 /* We defer the dereferences outside fo
206 if (!p->signal->leader) {
207 spin_unlock_irq(&p->sighand->siglock);
210 __group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p);
211 __group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p);
212 put_pid(p->signal->tty_old_pgrp); /* A noop */
213 spin_lock(&tty->ctrl_lock);
214 tty_pgrp = get_pid(tty->pgrp);
216 p->signal->tty_old_pgrp = get_pid(tty->pgrp);
217 spin_unlock(&tty->ctrl_lock);
218 spin_unlock_irq(&p->sighand->siglock);
219 } while_each_pid_task(tty->session, PIDTYPE_SID, p);
221 read_unlock(&tasklist_lock);
225 kill_pgrp(tty_pgrp, SIGHUP, exit_session);
233 * disassociate_ctty - disconnect controlling tty
234 * @on_exit: true if exiting so need to "hang up" the session
236 * This function is typically called only by the session leader, when
237 * it wants to disassociate itself from its controlling tty.
239 * It performs the following functions:
240 * (1) Sends a SIGHUP and SIGCONT to the foreground process group
241 * (2) Clears the tty from being controlling the session
242 * (3) Clears the controlling tty for all processes in the
245 * The argument on_exit is set to 1 if called when a process is
246 * exiting; it is 0 if called by the ioctl TIOCNOTTY.
249 * BTM is taken for hysterical raisons, and held when
250 * called from no_tty().
251 * tty_mutex is taken to protect tty
252 * ->siglock is taken to protect ->signal/->sighand
253 * tasklist_lock is taken to walk process list for sessions
254 * ->siglock is taken to protect ->signal/->sighand
256 void disassociate_ctty(int on_exit)
258 struct tty_struct *tty;
260 if (!current->signal->leader)
263 tty = get_current_tty();
265 if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY) {
266 tty_vhangup_session(tty);
268 struct pid *tty_pgrp = tty_get_pgrp(tty);
270 kill_pgrp(tty_pgrp, SIGHUP, on_exit);
272 kill_pgrp(tty_pgrp, SIGCONT, on_exit);
278 } else if (on_exit) {
279 struct pid *old_pgrp;
280 spin_lock_irq(¤t->sighand->siglock);
281 old_pgrp = current->signal->tty_old_pgrp;
282 current->signal->tty_old_pgrp = NULL;
283 spin_unlock_irq(¤t->sighand->siglock);
285 kill_pgrp(old_pgrp, SIGHUP, on_exit);
286 kill_pgrp(old_pgrp, SIGCONT, on_exit);
292 spin_lock_irq(¤t->sighand->siglock);
293 put_pid(current->signal->tty_old_pgrp);
294 current->signal->tty_old_pgrp = NULL;
295 tty = tty_kref_get(current->signal->tty);
296 spin_unlock_irq(¤t->sighand->siglock);
302 spin_lock_irqsave(&tty->ctrl_lock, flags);
303 put_pid(tty->session);
307 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
312 /* Now clear signal->tty under the lock */
313 read_lock(&tasklist_lock);
314 session_clear_tty(task_session(current));
315 read_unlock(&tasklist_lock);
320 * no_tty - Ensure the current process does not have a controlling tty
324 /* FIXME: Review locking here. The tty_lock never covered any race
325 between a new association and proc_clear_tty but possible we need
326 to protect against this anyway */
327 struct task_struct *tsk = current;
328 disassociate_ctty(0);
333 * tiocsctty - set controlling tty
334 * @tty: tty structure
335 * @arg: user argument
337 * This ioctl is used to manage job control. It permits a session
338 * leader to set this tty as the controlling tty for the session.
341 * Takes tty_lock() to serialize proc_set_tty() for this tty
342 * Takes tasklist_lock internally to walk sessions
343 * Takes ->siglock() when updating signal->tty
345 static int tiocsctty(struct tty_struct *tty, struct file *file, int arg)
350 read_lock(&tasklist_lock);
352 if (current->signal->leader && (task_session(current) == tty->session))
356 * The process must be a session leader and
357 * not have a controlling tty already.
359 if (!current->signal->leader || current->signal->tty) {
366 * This tty is already the controlling
367 * tty for another session group!
369 if (arg == 1 && capable(CAP_SYS_ADMIN)) {
373 session_clear_tty(tty->session);
380 /* See the comment in tty_open_proc_set_tty(). */
381 if ((file->f_mode & FMODE_READ) == 0 && !capable(CAP_SYS_ADMIN)) {
388 read_unlock(&tasklist_lock);
394 * tty_get_pgrp - return a ref counted pgrp pid
397 * Returns a refcounted instance of the pid struct for the process
398 * group controlling the tty.
400 struct pid *tty_get_pgrp(struct tty_struct *tty)
405 spin_lock_irqsave(&tty->ctrl_lock, flags);
406 pgrp = get_pid(tty->pgrp);
407 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
411 EXPORT_SYMBOL_GPL(tty_get_pgrp);
414 * This checks not only the pgrp, but falls back on the pid if no
415 * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
418 * The caller must hold rcu lock or the tasklist lock.
420 static struct pid *session_of_pgrp(struct pid *pgrp)
422 struct task_struct *p;
423 struct pid *sid = NULL;
425 p = pid_task(pgrp, PIDTYPE_PGID);
427 p = pid_task(pgrp, PIDTYPE_PID);
429 sid = task_session(p);
435 * tiocgpgrp - get process group
436 * @tty: tty passed by user
437 * @real_tty: tty side of the tty passed by the user if a pty else the tty
440 * Obtain the process group of the tty. If there is no process group
443 * Locking: none. Reference to current->signal->tty is safe.
445 static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
450 * (tty == real_tty) is a cheap way of
451 * testing if the tty is NOT a master pty.
453 if (tty == real_tty && current->signal->tty != real_tty)
455 pid = tty_get_pgrp(real_tty);
456 ret = put_user(pid_vnr(pid), p);
462 * tiocspgrp - attempt to set process group
463 * @tty: tty passed by user
464 * @real_tty: tty side device matching tty passed by user
467 * Set the process group of the tty to the session passed. Only
468 * permitted where the tty session is our session.
470 * Locking: RCU, ctrl lock
472 static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
476 int retval = tty_check_change(real_tty);
483 if (get_user(pgrp_nr, p))
488 spin_lock_irq(&real_tty->ctrl_lock);
489 if (!current->signal->tty ||
490 (current->signal->tty != real_tty) ||
491 (real_tty->session != task_session(current))) {
493 goto out_unlock_ctrl;
496 pgrp = find_vpid(pgrp_nr);
501 if (session_of_pgrp(pgrp) != task_session(current))
504 put_pid(real_tty->pgrp);
505 real_tty->pgrp = get_pid(pgrp);
509 spin_unlock_irq(&real_tty->ctrl_lock);
514 * tiocgsid - get session id
515 * @tty: tty passed by user
516 * @real_tty: tty side of the tty passed by the user if a pty else the tty
517 * @p: pointer to returned session id
519 * Obtain the session id of the tty. If there is no session
522 static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
528 * (tty == real_tty) is a cheap way of
529 * testing if the tty is NOT a master pty.
531 if (tty == real_tty && current->signal->tty != real_tty)
534 spin_lock_irqsave(&real_tty->ctrl_lock, flags);
535 if (!real_tty->session)
537 sid = pid_vnr(real_tty->session);
538 spin_unlock_irqrestore(&real_tty->ctrl_lock, flags);
540 return put_user(sid, p);
543 spin_unlock_irqrestore(&real_tty->ctrl_lock, flags);
548 * Called from tty_ioctl(). If tty is a pty then real_tty is the slave side,
549 * if not then tty == real_tty.
551 long tty_jobctrl_ioctl(struct tty_struct *tty, struct tty_struct *real_tty,
552 struct file *file, unsigned int cmd, unsigned long arg)
554 void __user *p = (void __user *)arg;
558 if (current->signal->tty != tty)
563 return tiocsctty(real_tty, file, arg);
565 return tiocgpgrp(tty, real_tty, p);
567 return tiocspgrp(tty, real_tty, p);
569 return tiocgsid(tty, real_tty, p);