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Commit 452a00d2 authored by Alan Cox's avatar Alan Cox Committed by Linus Torvalds
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tty: Make get_current_tty use a kref 



We now return a kref covered tty reference. That ensures the tty structure
doesn't go away when you have a return from get_current_tty. This is not
enough to protect you from most of the resources being freed behind your
back - yet.

[Updated to include fixes for SELinux problems found by Andrew Morton and
 an s390 leak found while debugging the former]

Signed-off-by: default avatarAlan Cox <alan@redhat.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f4d2a6c2

drivers/char/tty_io.c

+6 −4
Original line number Diff line number Diff line
@@ -786,12 +786,12 @@ void disassociate_ctty(int on_exit) 
	tty = get_current_tty();

	if (tty) {

		tty_pgrp = get_pid(tty->pgrp);

		lock_kernel();

		mutex_unlock(&tty_mutex);

		/* XXX: here we race, there is nothing protecting tty */

		lock_kernel();

		if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)

			tty_vhangup(tty);

		unlock_kernel();

		tty_kref_put(tty);

	} else if (on_exit) {

		struct pid *old_pgrp;

		spin_lock_irq(&current->sighand->siglock);
@@ -819,7 +819,6 @@ void disassociate_ctty(int on_exit) 
	spin_unlock_irq(&current->sighand->siglock);



	mutex_lock(&tty_mutex);

	/* It is possible that do_tty_hangup has free'd this tty */

	tty = get_current_tty();

	if (tty) {

		unsigned long flags;
@@ -829,6 +828,7 @@ void disassociate_ctty(int on_exit) 
		tty->session = NULL;

		tty->pgrp = NULL;

		spin_unlock_irqrestore(&tty->ctrl_lock, flags);

		tty_kref_put(tty);

	} else {

#ifdef TTY_DEBUG_HANGUP

		printk(KERN_DEBUG "error attempted to write to tty [0x%p]"
@@ -1806,6 +1806,8 @@ static int __tty_open(struct inode *inode, struct file *filp) 
		index = tty->index;

		filp->f_flags |= O_NONBLOCK; /* Don't let /dev/tty block */

		/* noctty = 1; */

		/* FIXME: Should we take a driver reference ? */

		tty_kref_put(tty);

		goto got_driver;

	}

#ifdef CONFIG_VT
@@ -3135,7 +3137,7 @@ struct tty_struct *get_current_tty(void) 
{

	struct tty_struct *tty;

	WARN_ON_ONCE(!mutex_is_locked(&tty_mutex));

	tty = current->signal->tty;

	tty = tty_kref_get(current->signal->tty);

	/*

	 * session->tty can be changed/cleared from under us, make sure we

	 * issue the load. The obtained pointer, when not NULL, is valid as

drivers/s390/char/fs3270.c

+2 −1
Original line number Diff line number Diff line
@@ -430,11 +430,12 @@ fs3270_open(struct inode *inode, struct file *filp) 
		mutex_lock(&tty_mutex);

		tty = get_current_tty();

		if (!tty || tty->driver->major != IBM_TTY3270_MAJOR) {

			mutex_unlock(&tty_mutex);

			tty_kref_put(tty);

			rc = -ENODEV;

			goto out;

		}

		minor = tty->index + RAW3270_FIRSTMINOR;

		tty_kref_put(tty);

		mutex_unlock(&tty_mutex);

	}

	/* Check if some other program is already using fullscreen mode. */

fs/dquot.c

+3 −3
Original line number Diff line number Diff line
@@ -897,8 +897,9 @@ static void print_warning(struct dquot *dquot, const int warntype) 


	mutex_lock(&tty_mutex);

	tty = get_current_tty();

	mutex_unlock(&tty_mutex);

	if (!tty)

		goto out_lock;

		return;

	tty_write_message(tty, dquot->dq_sb->s_id);

	if (warntype == QUOTA_NL_ISOFTWARN || warntype == QUOTA_NL_BSOFTWARN)

		tty_write_message(tty, ": warning, ");
@@ -926,8 +927,7 @@ static void print_warning(struct dquot *dquot, const int warntype) 
			break;

	}

	tty_write_message(tty, msg);

out_lock:

	mutex_unlock(&tty_mutex);

	tty_kref_put(tty);

}

#endif

security/selinux/hooks.c

+2 −1
Original line number Diff line number Diff line
@@ -2123,6 +2123,7 @@ static inline void flush_unauthorized_files(struct files_struct *files) 


	mutex_lock(&tty_mutex);

	tty = get_current_tty();

	mutex_unlock(&tty_mutex);

	if (tty) {

		file_list_lock();

		file = list_entry(tty->tty_files.next, typeof(*file), f_u.fu_list);
@@ -2139,8 +2140,8 @@ static inline void flush_unauthorized_files(struct files_struct *files) 
			}

		}

		file_list_unlock();

		tty_kref_put(tty);

	}

	mutex_unlock(&tty_mutex);

	/* Reset controlling tty. */

	if (drop_tty)

		no_tty();