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tty: split job control support into a file of its own

Browse Source 
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 <nico@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nicolas Pitre 2017-04-12 18:37:16 -04:00 committed by Greg Kroah-Hartman
parent fff0a2ca3a
commit a1235b3eb1
4 changed files with 572 additions and 537 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/tty/Makefile
View File

@ -1,6 +1,6 @@
obj-$(CONFIG_TTY) += tty_io.o n_tty.o tty_ioctl.o tty_ldisc.o \
tty_buffer.o tty_port.o tty_mutex.o \
tty_ldsem.o tty_baudrate.o
tty_ldsem.o tty_baudrate.o tty_jobctrl.o
obj-$(CONFIG_LEGACY_PTYS) += pty.o
obj-$(CONFIG_UNIX98_PTYS) += pty.o
obj-$(CONFIG_AUDIT) += tty_audit.o

547
drivers/tty/tty_io.c
View File

@ -377,65 +377,6 @@ struct tty_driver *tty_find_polling_driver(char *name, int *line)
EXPORT_SYMBOL_GPL(tty_find_polling_driver);
#endif
static int is_ignored(int sig)
{
return (sigismember(&current->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);
static ssize_t hung_up_tty_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
@ -509,79 +450,6 @@ static const struct file_operations hung_up_tty_fops = {
static DEFINE_SPINLOCK(redirect_lock);
static struct file *redirect;
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(&current->sighand->siglock);
__proc_set_tty(tty);
spin_unlock_irq(&current->sighand->siglock);
}
struct tty_struct *get_current_tty(void)
{
struct tty_struct *tty;
unsigned long flags;
spin_lock_irqsave(&current->sighand->siglock, flags);
tty = tty_kref_get(current->signal->tty);
spin_unlock_irqrestore(&current->sighand->siglock, flags);
return tty;
}
EXPORT_SYMBOL_GPL(get_current_tty);
static 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_wakeup - request more data
* @tty: terminal
@ -608,60 +476,6 @@ void tty_wakeup(struct tty_struct *tty)
EXPORT_SYMBOL_GPL(tty_wakeup);
/**
* 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.
*/
static 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;
}
/**
* __tty_hangup - actual handler for hangup events
* @work: tty device
@ -840,7 +654,7 @@ void tty_vhangup_self(void)
* is complete. That guarantee is necessary for security reasons.
*/
static void tty_vhangup_session(struct tty_struct *tty)
void tty_vhangup_session(struct tty_struct *tty)
{
tty_debug_hangup(tty, "session hangup\n");
__tty_hangup(tty, 1);
@ -861,106 +675,6 @@ int tty_hung_up_p(struct file *filp)
EXPORT_SYMBOL(tty_hung_up_p);
/**
* 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 raisins, 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(&current->sighand->siglock);
old_pgrp = current->signal->tty_old_pgrp;
current->signal->tty_old_pgrp = NULL;
spin_unlock_irq(&current->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(&current->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);
} else
tty_debug_hangup(tty, "no current tty\n");
spin_unlock_irq(&current->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);
}
/**
* stop_tty - propagate flow control
* @tty: tty to stop
@ -2163,38 +1877,13 @@ retry_open:
}
clear_bit(TTY_HUPPED, &tty->flags);
read_lock(&tasklist_lock);
spin_lock_irq(&current->sighand->siglock);
noctty = (filp->f_flags & O_NOCTTY) ||
(IS_ENABLED(CONFIG_VT) && device == MKDEV(TTY_MAJOR, 0)) ||
device == MKDEV(TTYAUX_MAJOR, 1) ||
(tty->driver->type == TTY_DRIVER_TYPE_PTY &&
tty->driver->subtype == PTY_TYPE_MASTER);
if (!noctty &&
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(&current->sighand->siglock);
read_unlock(&tasklist_lock);
(IS_ENABLED(CONFIG_VT) && device == MKDEV(TTY_MAJOR, 0)) ||
device == MKDEV(TTYAUX_MAJOR, 1) ||
(tty->driver->type == TTY_DRIVER_TYPE_PTY &&
tty->driver->subtype == PTY_TYPE_MASTER);
if (!noctty)
tty_open_proc_set_tty(filp, tty);
tty_unlock(tty);
return 0;
}
@ -2456,211 +2145,6 @@ static int fionbio(struct file *file, int __user *p)
return 0;
}
/**
* 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(). */
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);
}
/**
* tiocsetd - set line discipline
* @tty: tty device
@ -2920,19 +2404,6 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
int excl = test_bit(TTY_EXCLUSIVE, &tty->flags);
return put_user(excl, (int __user *)p);
}
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);
case TIOCGETD:
return tiocgetd(tty, p);
case TIOCSETD:
@ -2993,6 +2464,10 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
case TIOCSSERIAL:
tty_warn_deprecated_flags(p);
break;
default:
retval = tty_jobctrl_ioctl(tty, real_tty, file, cmd, arg);
if (retval != -ENOIOCTLCMD)
return retval;
}
if (tty->ops->ioctl) {
retval = tty->ops->ioctl(tty, cmd, arg);

554
drivers/tty/tty_jobctrl.c Normal file
View File

@ -0,0 +1,554 @@
/*
* 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(&current->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(&current->sighand->siglock);
__proc_set_tty(tty);
spin_unlock_irq(&current->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(&current->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(&current->sighand->siglock);
read_unlock(&tasklist_lock);
}
struct tty_struct *get_current_tty(void)
{
struct tty_struct *tty;
unsigned long flags;
spin_lock_irqsave(&current->sighand->siglock, flags);
tty = tty_kref_get(current->signal->tty);
spin_unlock_irqrestore(&current->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(&current->sighand->siglock);
old_pgrp = current->signal->tty_old_pgrp;
current->signal->tty_old_pgrp = NULL;
spin_unlock_irq(&current->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(&current->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(&current->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;
}

6
include/linux/tty.h
View File

@ -475,9 +475,13 @@ extern int tty_do_resize(struct tty_struct *tty, struct winsize *ws);
extern int is_current_pgrp_orphaned(void);
extern void tty_hangup(struct tty_struct *tty);
extern void tty_vhangup(struct tty_struct *tty);
extern void tty_vhangup_session(struct tty_struct *tty);
extern int tty_hung_up_p(struct file *filp);
extern void do_SAK(struct tty_struct *tty);
extern void __do_SAK(struct tty_struct *tty);
extern void tty_open_proc_set_tty(struct file *filp, struct tty_struct *tty);
extern int tty_signal_session_leader(struct tty_struct *tty, int exit_session);
extern void session_clear_tty(struct pid *session);
extern void no_tty(void);
extern void tty_buffer_free_all(struct tty_port *port);
extern void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld);
@ -525,6 +529,8 @@ extern void tty_ldisc_flush(struct tty_struct *tty);
extern long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
extern int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
unsigned int cmd, unsigned long arg);
extern long tty_jobctrl_ioctl(struct tty_struct *tty, struct tty_struct *real_tty,
struct file *file, unsigned int cmd, unsigned long arg);
extern int tty_perform_flush(struct tty_struct *tty, unsigned long arg);
extern void tty_default_fops(struct file_operations *fops);
extern struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx);