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Commit 4a510969 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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tty: Make tty_files_lock per-tty 



Access to tty->tty_files list is always per-tty, never for all ttys
simultaneously. Replace global tty_files_lock spinlock with per-tty
->files_lock. Initialize when the ->tty_files list is inited, in
alloc_tty_struct().

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 527ffc11

drivers/tty/tty_io.c

+12 −13
Original line number Diff line number Diff line
@@ -138,9 +138,6 @@ LIST_HEAD(tty_drivers); /* linked list of tty drivers */ 
/* Mutex to protect creating and releasing a tty */

DEFINE_MUTEX(tty_mutex);



/* Spinlock to protect the tty->tty_files list */

DEFINE_SPINLOCK(tty_files_lock);



static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);

static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);

ssize_t redirected_tty_write(struct file *, const char __user *,
@@ -202,9 +199,9 @@ void tty_add_file(struct tty_struct *tty, struct file *file) 
	priv->tty = tty;

	priv->file = file;



	spin_lock(&tty_files_lock);

	spin_lock(&tty->files_lock);

	list_add(&priv->list, &tty->tty_files);

	spin_unlock(&tty_files_lock);

	spin_unlock(&tty->files_lock);

}



/**
@@ -225,10 +222,11 @@ void tty_free_file(struct file *file) 
static void tty_del_file(struct file *file)

{

	struct tty_file_private *priv = file->private_data;

	struct tty_struct *tty = priv->tty;



	spin_lock(&tty_files_lock);

	spin_lock(&tty->files_lock);

	list_del(&priv->list);

	spin_unlock(&tty_files_lock);

	spin_unlock(&tty->files_lock);

	tty_free_file(file);

}
@@ -286,11 +284,11 @@ static int check_tty_count(struct tty_struct *tty, const char *routine) 
	struct list_head *p;

	int count = 0;



	spin_lock(&tty_files_lock);

	spin_lock(&tty->files_lock);

	list_for_each(p, &tty->tty_files) {

		count++;

	}

	spin_unlock(&tty_files_lock);

	spin_unlock(&tty->files_lock);

	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&

	    tty->driver->subtype == PTY_TYPE_SLAVE &&

	    tty->link && tty->link->count)
@@ -713,7 +711,7 @@ static void __tty_hangup(struct tty_struct *tty, int exit_session) 
	   workqueue with the lock held */

	check_tty_count(tty, "tty_hangup");



	spin_lock(&tty_files_lock);

	spin_lock(&tty->files_lock);

	/* This breaks for file handles being sent over AF_UNIX sockets ? */

	list_for_each_entry(priv, &tty->tty_files, list) {

		filp = priv->file;
@@ -725,7 +723,7 @@ static void __tty_hangup(struct tty_struct *tty, int exit_session) 
		__tty_fasync(-1, filp, 0);	/* can't block */

		filp->f_op = &hung_up_tty_fops;

	}

	spin_unlock(&tty_files_lock);

	spin_unlock(&tty->files_lock);



	refs = tty_signal_session_leader(tty, exit_session);

	/* Account for the p->signal references we killed */
@@ -1637,9 +1635,9 @@ static void release_one_tty(struct work_struct *work) 
	tty_driver_kref_put(driver);

	module_put(owner);



	spin_lock(&tty_files_lock);

	spin_lock(&tty->files_lock);

	list_del_init(&tty->tty_files);

	spin_unlock(&tty_files_lock);

	spin_unlock(&tty->files_lock);



	put_pid(tty->pgrp);

	put_pid(tty->session);
@@ -3176,6 +3174,7 @@ struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx) 
	mutex_init(&tty->atomic_write_lock);

	spin_lock_init(&tty->ctrl_lock);

	spin_lock_init(&tty->flow_lock);

	spin_lock_init(&tty->files_lock);

	INIT_LIST_HEAD(&tty->tty_files);

	INIT_WORK(&tty->SAK_work, do_SAK_work);

include/linux/tty.h

+1 −1
Original line number Diff line number Diff line
@@ -302,6 +302,7 @@ struct tty_struct { 
	struct work_struct hangup_work;

	void *disc_data;

	void *driver_data;

	spinlock_t files_lock;		/* protects tty_files list */

	struct list_head tty_files;



#define N_TTY_BUF_SIZE 4096
@@ -508,7 +509,6 @@ extern int tty_standard_install(struct tty_driver *driver, 
		struct tty_struct *tty);



extern struct mutex tty_mutex;

extern spinlock_t tty_files_lock;



#define tty_is_writelocked(tty)  (mutex_is_locked(&tty->atomic_write_lock))

security/selinux/hooks.c

+2 −2
Original line number Diff line number Diff line
@@ -2415,7 +2415,7 @@ static inline void flush_unauthorized_files(const struct cred *cred, 


	tty = get_current_tty();

	if (tty) {

		spin_lock(&tty_files_lock);

		spin_lock(&tty->files_lock);

		if (!list_empty(&tty->tty_files)) {

			struct tty_file_private *file_priv;
@@ -2430,7 +2430,7 @@ static inline void flush_unauthorized_files(const struct cred *cred, 
			if (file_path_has_perm(cred, file, FILE__READ | FILE__WRITE))

				drop_tty = 1;

		}

		spin_unlock(&tty_files_lock);

		spin_unlock(&tty->files_lock);

		tty_kref_put(tty);

	}

	/* Reset controlling tty. */