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redo locking of tty->pgrp

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Historically tty->pgrp and friends were pid_t and the code "knew" they were
safe.  The change to pid structs opened up a few races and the removal of the
BKL in places made them quite hittable.  We put tty->pgrp under the ctrl_lock
for the tty.

Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alan Cox 2008-04-30 00:53:30 -07:00 committed by Linus Torvalds
parent 04f378b198
commit 47f86834bb
3 changed files with 72 additions and 22 deletions
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78
drivers/char/tty_io.c
View File

@ -1204,26 +1204,37 @@ EXPORT_SYMBOL_GPL(tty_find_polling_driver);
* not in the foreground, send a SIGTTOU. If the signal is blocked or
* ignored, go ahead and perform the operation. (POSIX 7.2)
*
* Locking: none - FIXME: review this
* Locking: ctrl_lock - FIXME: review this
*/
int tty_check_change(struct tty_struct *tty)
{
unsigned long flags;
int ret = 0;
if (current->signal->tty != tty)
return 0;
spin_lock_irqsave(&tty->ctrl_lock, flags);
if (!tty->pgrp) {
printk(KERN_WARNING "tty_check_change: tty->pgrp == NULL!\n");
return 0;
goto out;
}
if (task_pgrp(current) == tty->pgrp)
return 0;
goto out;
if (is_ignored(SIGTTOU))
return 0;
if (is_current_pgrp_orphaned())
return -EIO;
goto out;
if (is_current_pgrp_orphaned()) {
ret = -EIO;
goto out;
}
kill_pgrp(task_pgrp(current), SIGTTOU, 1);
set_thread_flag(TIF_SIGPENDING);
return -ERESTARTSYS;
ret = -ERESTARTSYS;
out:
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
return ret;
}
EXPORT_SYMBOL(tty_check_change);
@ -1403,6 +1414,7 @@ static void do_tty_hangup(struct work_struct *work)
struct task_struct *p;
struct tty_ldisc *ld;
int closecount = 0, n;
unsigned long flags;
if (!tty)
return;
@ -1479,19 +1491,24 @@ static void do_tty_hangup(struct work_struct *work)
__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_irqsave(&tty->ctrl_lock, flags);
if (tty->pgrp)
p->signal->tty_old_pgrp = get_pid(tty->pgrp);
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
spin_unlock_irq(&p->sighand->siglock);
} while_each_pid_task(tty->session, PIDTYPE_SID, p);
}
read_unlock(&tasklist_lock);
spin_lock_irqsave(&tty->ctrl_lock, flags);
tty->flags = 0;
put_pid(tty->session);
put_pid(tty->pgrp);
tty->session = NULL;
tty->pgrp = NULL;
tty->ctrl_status = 0;
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
/*
* If one of the devices matches a console pointer, we
* cannot just call hangup() because that will cause
@ -1666,10 +1683,13 @@ void disassociate_ctty(int on_exit)
/* It is possible that do_tty_hangup has free'd this tty */
tty = get_current_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);
} else {
#ifdef TTY_DEBUG_HANGUP
printk(KERN_DEBUG "error attempted to write to tty [0x%p]"
@ -1785,10 +1805,8 @@ EXPORT_SYMBOL(start_tty);
* for hung up devices before calling the line discipline method.
*
* Locking:
* Locks the line discipline internally while needed
* For historical reasons the line discipline read method is
* invoked under the BKL. This will go away in time so do not rely on it
* in new code. Multiple read calls may be outstanding in parallel.
* Locks the line discipline internally while needed. Multiple
* read calls may be outstanding in parallel.
*/
static ssize_t tty_read(struct file *file, char __user *buf, size_t count,
@ -2888,6 +2906,7 @@ static unsigned int tty_poll(struct file *filp, poll_table *wait)
static int tty_fasync(int fd, struct file *filp, int on)
{
struct tty_struct *tty;
unsigned long flags;
int retval;
tty = (struct tty_struct *)filp->private_data;
@ -2903,6 +2922,7 @@ static int tty_fasync(int fd, struct file *filp, int on)
struct pid *pid;
if (!waitqueue_active(&tty->read_wait))
tty->minimum_to_wake = 1;
spin_lock_irqsave(&tty->ctrl_lock, flags);
if (tty->pgrp) {
pid = tty->pgrp;
type = PIDTYPE_PGID;
@ -2910,6 +2930,7 @@ static int tty_fasync(int fd, struct file *filp, int on)
pid = task_pid(current);
type = PIDTYPE_PID;
}
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
retval = __f_setown(filp, pid, type, 0);
if (retval)
return retval;
@ -2995,6 +3016,8 @@ static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
struct winsize __user *arg)
{
struct winsize tmp_ws;
struct pid *pgrp, *rpgrp;
unsigned long flags;
if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
return -EFAULT;
@ -3012,10 +3035,21 @@ static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
}
}
#endif
if (tty->pgrp)
kill_pgrp(tty->pgrp, SIGWINCH, 1);
if ((real_tty->pgrp != tty->pgrp) && real_tty->pgrp)
kill_pgrp(real_tty->pgrp, SIGWINCH, 1);
/* Get the PID values and reference them so we can
avoid holding the tty ctrl lock while sending signals */
spin_lock_irqsave(&tty->ctrl_lock, flags);
pgrp = get_pid(tty->pgrp);
rpgrp = get_pid(real_tty->pgrp);
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
if (pgrp)
kill_pgrp(pgrp, SIGWINCH, 1);
if (rpgrp != pgrp && rpgrp)
kill_pgrp(rpgrp, SIGWINCH, 1);
put_pid(pgrp);
put_pid(rpgrp);
tty->winsize = tmp_ws;
real_tty->winsize = tmp_ws;
done:
@ -3171,7 +3205,7 @@ static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
* Set the process group of the tty to the session passed. Only
* permitted where the tty session is our session.
*
* Locking: RCU
* Locking: RCU, ctrl lock
*/
static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
@ -3179,6 +3213,7 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
struct pid *pgrp;
pid_t pgrp_nr;
int retval = tty_check_change(real_tty);
unsigned long flags;
if (retval == -EIO)
return -ENOTTY;
@ -3201,8 +3236,10 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
if (session_of_pgrp(pgrp) != task_session(current))
goto out_unlock;
retval = 0;
spin_lock_irqsave(&tty->ctrl_lock, flags);
put_pid(real_tty->pgrp);
real_tty->pgrp = get_pid(pgrp);
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
out_unlock:
rcu_read_unlock();
return retval;
@ -4077,14 +4114,19 @@ void proc_clear_tty(struct task_struct *p)
}
EXPORT_SYMBOL(proc_clear_tty);
/* Called under the sighand lock */
static void __proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
{
if (tty) {
/* We should not have a session or pgrp to here but.... */
unsigned long flags;
/* We should not have a session or pgrp to put here but.... */
spin_lock_irqsave(&tty->ctrl_lock, flags);
put_pid(tty->session);
put_pid(tty->pgrp);
tty->session = get_pid(task_session(tsk));
tty->pgrp = get_pid(task_pgrp(tsk));
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
tty->session = get_pid(task_session(tsk));
}
put_pid(tsk->signal->tty_old_pgrp);
tsk->signal->tty = tty;

6
drivers/char/vt.c
View File

@ -909,15 +909,21 @@ int vc_resize(struct vc_data *vc, unsigned int cols, unsigned int lines)
if (vc->vc_tty) {
struct winsize ws, *cws = &vc->vc_tty->winsize;
unsigned long flags;
memset(&ws, 0, sizeof(ws));
ws.ws_row = vc->vc_rows;
ws.ws_col = vc->vc_cols;
ws.ws_ypixel = vc->vc_scan_lines;
mutex_lock(&vc->vc_tty->termios_mutex);
spin_lock_irqsave(&vc->vc_tty->ctrl_lock, flags);
if ((ws.ws_row != cws->ws_row || ws.ws_col != cws->ws_col) &&
vc->vc_tty->pgrp)
kill_pgrp(vc->vc_tty->pgrp, SIGWINCH, 1);
spin_unlock_irqrestore(&vc->vc_tty->ctrl_lock, flags);
*cws = ws;
mutex_unlock(&vc->vc_tty->termios_mutex);
}
if (CON_IS_VISIBLE(vc))

10
include/linux/tty.h
View File

@ -184,21 +184,22 @@ struct tty_struct {
struct tty_ldisc ldisc;
struct mutex termios_mutex;
spinlock_t ctrl_lock;
/* Termios values are protected by the termios mutex */
struct ktermios *termios, *termios_locked;
char name[64];
struct pid *pgrp;
struct pid *pgrp; /* Protected by ctrl lock */
struct pid *session;
unsigned long flags;
int count;
struct winsize winsize;
struct winsize winsize; /* termios mutex */
unsigned char stopped:1, hw_stopped:1, flow_stopped:1, packet:1;
unsigned char low_latency:1, warned:1;
unsigned char ctrl_status;
unsigned char ctrl_status; /* ctrl_lock */
unsigned int receive_room; /* Bytes free for queue */
struct tty_struct *link;
struct fasync_struct *fasync;
struct tty_bufhead buf;
struct tty_bufhead buf; /* Locked internally */
int alt_speed; /* For magic substitution of 38400 bps */
wait_queue_head_t write_wait;
wait_queue_head_t read_wait;
@ -212,6 +213,7 @@ struct tty_struct {
/*
* The following is data for the N_TTY line discipline. For
* historical reasons, this is included in the tty structure.
* Mostly locked by the BKL.
*/
unsigned int column;
unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;