From a1235b3eb10086b8420f37bbb6c29436f55940ba Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Wed, 12 Apr 2017 18:37:16 -0400 Subject: tty: split job control support into a file of its own This makes it easier for job control to become optional and/or usable independently from tty_io.c, as well as providing a nice purpose separation. No logical changes from this patch. Signed-off-by: Nicolas Pitre Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_jobctrl.c | 554 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 554 insertions(+) create mode 100644 drivers/tty/tty_jobctrl.c (limited to 'drivers/tty/tty_jobctrl.c') diff --git a/drivers/tty/tty_jobctrl.c b/drivers/tty/tty_jobctrl.c new file mode 100644 index 000000000000..e7032309ee87 --- /dev/null +++ b/drivers/tty/tty_jobctrl.c @@ -0,0 +1,554 @@ +/* + * Copyright (C) 1991, 1992 Linus Torvalds + */ + +#include +#include +#include +#include +#include +#include +#include +#include + +static int is_ignored(int sig) +{ + return (sigismember(¤t->blocked, sig) || + current->sighand->action[sig-1].sa.sa_handler == SIG_IGN); +} + +/** + * tty_check_change - check for POSIX terminal changes + * @tty: tty to check + * + * If we try to write to, or set the state of, a terminal and we're + * not in the foreground, send a SIGTTOU. If the signal is blocked or + * ignored, go ahead and perform the operation. (POSIX 7.2) + * + * Locking: ctrl_lock + */ +int __tty_check_change(struct tty_struct *tty, int sig) +{ + unsigned long flags; + struct pid *pgrp, *tty_pgrp; + int ret = 0; + + if (current->signal->tty != tty) + return 0; + + rcu_read_lock(); + pgrp = task_pgrp(current); + + spin_lock_irqsave(&tty->ctrl_lock, flags); + tty_pgrp = tty->pgrp; + spin_unlock_irqrestore(&tty->ctrl_lock, flags); + + if (tty_pgrp && pgrp != tty->pgrp) { + if (is_ignored(sig)) { + if (sig == SIGTTIN) + ret = -EIO; + } else if (is_current_pgrp_orphaned()) + ret = -EIO; + else { + kill_pgrp(pgrp, sig, 1); + set_thread_flag(TIF_SIGPENDING); + ret = -ERESTARTSYS; + } + } + rcu_read_unlock(); + + if (!tty_pgrp) + tty_warn(tty, "sig=%d, tty->pgrp == NULL!\n", sig); + + return ret; +} + +int tty_check_change(struct tty_struct *tty) +{ + return __tty_check_change(tty, SIGTTOU); +} +EXPORT_SYMBOL(tty_check_change); + +void proc_clear_tty(struct task_struct *p) +{ + unsigned long flags; + struct tty_struct *tty; + spin_lock_irqsave(&p->sighand->siglock, flags); + tty = p->signal->tty; + p->signal->tty = NULL; + spin_unlock_irqrestore(&p->sighand->siglock, flags); + tty_kref_put(tty); +} + +/** + * proc_set_tty - set the controlling terminal + * + * Only callable by the session leader and only if it does not already have + * a controlling terminal. + * + * Caller must hold: tty_lock() + * a readlock on tasklist_lock + * sighand lock + */ +static void __proc_set_tty(struct tty_struct *tty) +{ + unsigned long flags; + + spin_lock_irqsave(&tty->ctrl_lock, flags); + /* + * The session and fg pgrp references will be non-NULL if + * tiocsctty() is stealing the controlling tty + */ + put_pid(tty->session); + put_pid(tty->pgrp); + tty->pgrp = get_pid(task_pgrp(current)); + spin_unlock_irqrestore(&tty->ctrl_lock, flags); + tty->session = get_pid(task_session(current)); + if (current->signal->tty) { + tty_debug(tty, "current tty %s not NULL!!\n", + current->signal->tty->name); + tty_kref_put(current->signal->tty); + } + put_pid(current->signal->tty_old_pgrp); + current->signal->tty = tty_kref_get(tty); + current->signal->tty_old_pgrp = NULL; +} + +static void proc_set_tty(struct tty_struct *tty) +{ + spin_lock_irq(¤t->sighand->siglock); + __proc_set_tty(tty); + spin_unlock_irq(¤t->sighand->siglock); +} + +/* + * Called by tty_open() to set the controlling tty if applicable. + */ +void tty_open_proc_set_tty(struct file *filp, struct tty_struct *tty) +{ + read_lock(&tasklist_lock); + spin_lock_irq(¤t->sighand->siglock); + if (current->signal->leader && + !current->signal->tty && + tty->session == NULL) { + /* + * Don't let a process that only has write access to the tty + * obtain the privileges associated with having a tty as + * controlling terminal (being able to reopen it with full + * access through /dev/tty, being able to perform pushback). + * Many distributions set the group of all ttys to "tty" and + * grant write-only access to all terminals for setgid tty + * binaries, which should not imply full privileges on all ttys. + * + * This could theoretically break old code that performs open() + * on a write-only file descriptor. In that case, it might be + * necessary to also permit this if + * inode_permission(inode, MAY_READ) == 0. + */ + if (filp->f_mode & FMODE_READ) + __proc_set_tty(tty); + } + spin_unlock_irq(¤t->sighand->siglock); + read_unlock(&tasklist_lock); +} + +struct tty_struct *get_current_tty(void) +{ + struct tty_struct *tty; + unsigned long flags; + + spin_lock_irqsave(¤t->sighand->siglock, flags); + tty = tty_kref_get(current->signal->tty); + spin_unlock_irqrestore(¤t->sighand->siglock, flags); + return tty; +} +EXPORT_SYMBOL_GPL(get_current_tty); + +/* + * Called from tty_release(). + */ +void session_clear_tty(struct pid *session) +{ + struct task_struct *p; + do_each_pid_task(session, PIDTYPE_SID, p) { + proc_clear_tty(p); + } while_each_pid_task(session, PIDTYPE_SID, p); +} + +/** + * tty_signal_session_leader - sends SIGHUP to session leader + * @tty controlling tty + * @exit_session if non-zero, signal all foreground group processes + * + * Send SIGHUP and SIGCONT to the session leader and its process group. + * Optionally, signal all processes in the foreground process group. + * + * Returns the number of processes in the session with this tty + * as their controlling terminal. This value is used to drop + * tty references for those processes. + */ +int tty_signal_session_leader(struct tty_struct *tty, int exit_session) +{ + struct task_struct *p; + int refs = 0; + struct pid *tty_pgrp = NULL; + + read_lock(&tasklist_lock); + if (tty->session) { + do_each_pid_task(tty->session, PIDTYPE_SID, p) { + spin_lock_irq(&p->sighand->siglock); + if (p->signal->tty == tty) { + p->signal->tty = NULL; + /* We defer the dereferences outside fo + the tasklist lock */ + refs++; + } + if (!p->signal->leader) { + spin_unlock_irq(&p->sighand->siglock); + continue; + } + __group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p); + __group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p); + put_pid(p->signal->tty_old_pgrp); /* A noop */ + spin_lock(&tty->ctrl_lock); + tty_pgrp = get_pid(tty->pgrp); + if (tty->pgrp) + p->signal->tty_old_pgrp = get_pid(tty->pgrp); + spin_unlock(&tty->ctrl_lock); + spin_unlock_irq(&p->sighand->siglock); + } while_each_pid_task(tty->session, PIDTYPE_SID, p); + } + read_unlock(&tasklist_lock); + + if (tty_pgrp) { + if (exit_session) + kill_pgrp(tty_pgrp, SIGHUP, exit_session); + put_pid(tty_pgrp); + } + + return refs; +} + +/** + * disassociate_ctty - disconnect controlling tty + * @on_exit: true if exiting so need to "hang up" the session + * + * This function is typically called only by the session leader, when + * it wants to disassociate itself from its controlling tty. + * + * It performs the following functions: + * (1) Sends a SIGHUP and SIGCONT to the foreground process group + * (2) Clears the tty from being controlling the session + * (3) Clears the controlling tty for all processes in the + * session group. + * + * The argument on_exit is set to 1 if called when a process is + * exiting; it is 0 if called by the ioctl TIOCNOTTY. + * + * Locking: + * BTM is taken for hysterical raisons, and held when + * called from no_tty(). + * tty_mutex is taken to protect tty + * ->siglock is taken to protect ->signal/->sighand + * tasklist_lock is taken to walk process list for sessions + * ->siglock is taken to protect ->signal/->sighand + */ +void disassociate_ctty(int on_exit) +{ + struct tty_struct *tty; + + if (!current->signal->leader) + return; + + tty = get_current_tty(); + if (tty) { + if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY) { + tty_vhangup_session(tty); + } else { + struct pid *tty_pgrp = tty_get_pgrp(tty); + if (tty_pgrp) { + kill_pgrp(tty_pgrp, SIGHUP, on_exit); + if (!on_exit) + kill_pgrp(tty_pgrp, SIGCONT, on_exit); + put_pid(tty_pgrp); + } + } + tty_kref_put(tty); + + } else if (on_exit) { + struct pid *old_pgrp; + spin_lock_irq(¤t->sighand->siglock); + old_pgrp = current->signal->tty_old_pgrp; + current->signal->tty_old_pgrp = NULL; + spin_unlock_irq(¤t->sighand->siglock); + if (old_pgrp) { + kill_pgrp(old_pgrp, SIGHUP, on_exit); + kill_pgrp(old_pgrp, SIGCONT, on_exit); + put_pid(old_pgrp); + } + return; + } + + spin_lock_irq(¤t->sighand->siglock); + put_pid(current->signal->tty_old_pgrp); + current->signal->tty_old_pgrp = NULL; + + tty = tty_kref_get(current->signal->tty); + if (tty) { + unsigned long flags; + spin_lock_irqsave(&tty->ctrl_lock, flags); + put_pid(tty->session); + put_pid(tty->pgrp); + tty->session = NULL; + tty->pgrp = NULL; + spin_unlock_irqrestore(&tty->ctrl_lock, flags); + tty_kref_put(tty); + } + + spin_unlock_irq(¤t->sighand->siglock); + /* Now clear signal->tty under the lock */ + read_lock(&tasklist_lock); + session_clear_tty(task_session(current)); + read_unlock(&tasklist_lock); +} + +/** + * + * no_tty - Ensure the current process does not have a controlling tty + */ +void no_tty(void) +{ + /* FIXME: Review locking here. The tty_lock never covered any race + between a new association and proc_clear_tty but possible we need + to protect against this anyway */ + struct task_struct *tsk = current; + disassociate_ctty(0); + proc_clear_tty(tsk); +} + +/** + * tiocsctty - set controlling tty + * @tty: tty structure + * @arg: user argument + * + * This ioctl is used to manage job control. It permits a session + * leader to set this tty as the controlling tty for the session. + * + * Locking: + * Takes tty_lock() to serialize proc_set_tty() for this tty + * Takes tasklist_lock internally to walk sessions + * Takes ->siglock() when updating signal->tty + */ +static int tiocsctty(struct tty_struct *tty, struct file *file, int arg) +{ + int ret = 0; + + tty_lock(tty); + read_lock(&tasklist_lock); + + if (current->signal->leader && (task_session(current) == tty->session)) + goto unlock; + + /* + * The process must be a session leader and + * not have a controlling tty already. + */ + if (!current->signal->leader || current->signal->tty) { + ret = -EPERM; + goto unlock; + } + + if (tty->session) { + /* + * This tty is already the controlling + * tty for another session group! + */ + if (arg == 1 && capable(CAP_SYS_ADMIN)) { + /* + * Steal it away + */ + session_clear_tty(tty->session); + } else { + ret = -EPERM; + goto unlock; + } + } + + /* See the comment in tty_open_proc_set_tty(). */ + if ((file->f_mode & FMODE_READ) == 0 && !capable(CAP_SYS_ADMIN)) { + ret = -EPERM; + goto unlock; + } + + proc_set_tty(tty); +unlock: + read_unlock(&tasklist_lock); + tty_unlock(tty); + return ret; +} + +/** + * 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. + */ +struct pid *tty_get_pgrp(struct tty_struct *tty) +{ + unsigned long flags; + struct pid *pgrp; + + spin_lock_irqsave(&tty->ctrl_lock, flags); + pgrp = get_pid(tty->pgrp); + spin_unlock_irqrestore(&tty->ctrl_lock, flags); + + return pgrp; +} +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. + */ +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; +} + +/** + * 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; +} + +/** + * 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 (!current->signal->tty || + (current->signal->tty != real_tty) || + (real_tty->session != task_session(current))) + return -ENOTTY; + if (get_user(pgrp_nr, p)) + return -EFAULT; + if (pgrp_nr < 0) + return -EINVAL; + 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; + spin_lock_irq(&tty->ctrl_lock); + put_pid(real_tty->pgrp); + real_tty->pgrp = get_pid(pgrp); + spin_unlock_irq(&tty->ctrl_lock); +out_unlock: + rcu_read_unlock(); + 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. + * + * Locking: none. Reference to current->signal->tty is safe. + */ +static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p) +{ + /* + * (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; + if (!real_tty->session) + return -ENOTTY; + return put_user(pid_vnr(real_tty->session), p); +} + +/* + * 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; +} -- cgit