v4.19.13 snapshot.
diff --git a/drivers/tty/tty_jobctrl.c b/drivers/tty/tty_jobctrl.c
new file mode 100644
index 0000000..c4ecd66
--- /dev/null
+++ b/drivers/tty/tty_jobctrl.c
@@ -0,0 +1,555 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ */
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/signal.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/task.h>
+#include <linux/tty.h>
+#include <linux/fcntl.h>
+#include <linux/uaccess.h>
+
+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;
+}