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path: root/drivers/tty/tty_io.c
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Diffstat (limited to 'drivers/tty/tty_io.c')
-rw-r--r--drivers/tty/tty_io.c76
1 files changed, 47 insertions, 29 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index d939bd705c7..9e930c009bf 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -185,6 +185,7 @@ void free_tty_struct(struct tty_struct *tty)
put_device(tty->dev);
kfree(tty->write_buf);
tty_buffer_free_all(tty);
+ tty->magic = 0xDEADDEAD;
kfree(tty);
}
@@ -573,7 +574,7 @@ void __tty_hangup(struct tty_struct *tty)
}
spin_unlock(&redirect_lock);
- tty_lock();
+ tty_lock(tty);
/* some functions below drop BTM, so we need this bit */
set_bit(TTY_HUPPING, &tty->flags);
@@ -666,7 +667,7 @@ void __tty_hangup(struct tty_struct *tty)
clear_bit(TTY_HUPPING, &tty->flags);
tty_ldisc_enable(tty);
- tty_unlock();
+ tty_unlock(tty);
if (f)
fput(f);
@@ -855,10 +856,11 @@ void disassociate_ctty(int on_exit)
*/
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;
- tty_lock();
disassociate_ctty(0);
- tty_unlock();
proc_clear_tty(tsk);
}
@@ -1102,12 +1104,12 @@ void tty_write_message(struct tty_struct *tty, char *msg)
{
if (tty) {
mutex_lock(&tty->atomic_write_lock);
- tty_lock();
+ tty_lock(tty);
if (tty->ops->write && !test_bit(TTY_CLOSING, &tty->flags)) {
- tty_unlock();
+ tty_unlock(tty);
tty->ops->write(tty, msg, strlen(msg));
} else
- tty_unlock();
+ tty_unlock(tty);
tty_write_unlock(tty);
}
return;
@@ -1402,6 +1404,7 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
}
initialize_tty_struct(tty, driver, idx);
+ tty_lock(tty);
retval = tty_driver_install_tty(driver, tty);
if (retval < 0)
goto err_deinit_tty;
@@ -1414,9 +1417,11 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
retval = tty_ldisc_setup(tty, tty->link);
if (retval)
goto err_release_tty;
+ /* Return the tty locked so that it cannot vanish under the caller */
return tty;
err_deinit_tty:
+ tty_unlock(tty);
deinitialize_tty_struct(tty);
free_tty_struct(tty);
err_module_put:
@@ -1425,6 +1430,7 @@ err_module_put:
/* call the tty release_tty routine to clean out this slot */
err_release_tty:
+ tty_unlock(tty);
printk_ratelimited(KERN_INFO "tty_init_dev: ldisc open failed, "
"clearing slot %d\n", idx);
release_tty(tty, idx);
@@ -1627,7 +1633,7 @@ int tty_release(struct inode *inode, struct file *filp)
if (tty_paranoia_check(tty, inode, __func__))
return 0;
- tty_lock();
+ tty_lock(tty);
check_tty_count(tty, __func__);
__tty_fasync(-1, filp, 0);
@@ -1636,10 +1642,11 @@ int tty_release(struct inode *inode, struct file *filp)
pty_master = (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
tty->driver->subtype == PTY_TYPE_MASTER);
devpts = (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM) != 0;
+ /* Review: parallel close */
o_tty = tty->link;
if (tty_release_checks(tty, o_tty, idx)) {
- tty_unlock();
+ tty_unlock(tty);
return 0;
}
@@ -1651,7 +1658,7 @@ int tty_release(struct inode *inode, struct file *filp)
if (tty->ops->close)
tty->ops->close(tty, filp);
- tty_unlock();
+ tty_unlock(tty);
/*
* Sanity check: if tty->count is going to zero, there shouldn't be
* any waiters on tty->read_wait or tty->write_wait. We test the
@@ -1674,7 +1681,7 @@ int tty_release(struct inode *inode, struct file *filp)
opens on /dev/tty */
mutex_lock(&tty_mutex);
- tty_lock();
+ tty_lock_pair(tty, o_tty);
tty_closing = tty->count <= 1;
o_tty_closing = o_tty &&
(o_tty->count <= (pty_master ? 1 : 0));
@@ -1705,7 +1712,7 @@ int tty_release(struct inode *inode, struct file *filp)
printk(KERN_WARNING "%s: %s: read/write wait queue active!\n",
__func__, tty_name(tty, buf));
- tty_unlock();
+ tty_unlock_pair(tty, o_tty);
mutex_unlock(&tty_mutex);
schedule();
}
@@ -1768,7 +1775,7 @@ int tty_release(struct inode *inode, struct file *filp)
/* check whether both sides are closing ... */
if (!tty_closing || (o_tty && !o_tty_closing)) {
- tty_unlock();
+ tty_unlock_pair(tty, o_tty);
return 0;
}
@@ -1781,14 +1788,16 @@ int tty_release(struct inode *inode, struct file *filp)
tty_ldisc_release(tty, o_tty);
/*
* The release_tty function takes care of the details of clearing
- * the slots and preserving the termios structure.
+ * the slots and preserving the termios structure. The tty_unlock_pair
+ * should be safe as we keep a kref while the tty is locked (so the
+ * unlock never unlocks a freed tty).
*/
release_tty(tty, idx);
+ tty_unlock_pair(tty, o_tty);
/* Make this pty number available for reallocation */
if (devpts)
devpts_kill_index(inode, idx);
- tty_unlock();
return 0;
}
@@ -1800,6 +1809,9 @@ int tty_release(struct inode *inode, struct file *filp)
*
* We cannot return driver and index like for the other nodes because
* devpts will not work then. It expects inodes to be from devpts FS.
+ *
+ * We need to move to returning a refcounted object from all the lookup
+ * paths including this one.
*/
static struct tty_struct *tty_open_current_tty(dev_t device, struct file *filp)
{
@@ -1816,6 +1828,7 @@ static struct tty_struct *tty_open_current_tty(dev_t device, struct file *filp)
/* noctty = 1; */
tty_kref_put(tty);
/* FIXME: we put a reference and return a TTY! */
+ /* This is only safe because the caller holds tty_mutex */
return tty;
}
@@ -1888,6 +1901,9 @@ static struct tty_driver *tty_lookup_driver(dev_t device, struct file *filp,
* Locking: tty_mutex protects tty, tty_lookup_driver and tty_init_dev.
* tty->count should protect the rest.
* ->siglock protects ->signal/->sighand
+ *
+ * Note: the tty_unlock/lock cases without a ref are only safe due to
+ * tty_mutex
*/
static int tty_open(struct inode *inode, struct file *filp)
@@ -1911,8 +1927,7 @@ retry_open:
retval = 0;
mutex_lock(&tty_mutex);
- tty_lock();
-
+ /* This is protected by the tty_mutex */
tty = tty_open_current_tty(device, filp);
if (IS_ERR(tty)) {
retval = PTR_ERR(tty);
@@ -1933,17 +1948,19 @@ retry_open:
}
if (tty) {
+ tty_lock(tty);
retval = tty_reopen(tty);
- if (retval)
+ if (retval < 0) {
+ tty_unlock(tty);
tty = ERR_PTR(retval);
- } else
+ }
+ } else /* Returns with the tty_lock held for now */
tty = tty_init_dev(driver, index);
mutex_unlock(&tty_mutex);
if (driver)
tty_driver_kref_put(driver);
if (IS_ERR(tty)) {
- tty_unlock();
retval = PTR_ERR(tty);
goto err_file;
}
@@ -1972,7 +1989,7 @@ retry_open:
printk(KERN_DEBUG "%s: error %d in opening %s...\n", __func__,
retval, tty->name);
#endif
- tty_unlock(); /* need to call tty_release without BTM */
+ tty_unlock(tty); /* need to call tty_release without BTM */
tty_release(inode, filp);
if (retval != -ERESTARTSYS)
return retval;
@@ -1984,17 +2001,15 @@ retry_open:
/*
* Need to reset f_op in case a hangup happened.
*/
- tty_lock();
if (filp->f_op == &hung_up_tty_fops)
filp->f_op = &tty_fops;
- tty_unlock();
goto retry_open;
}
- tty_unlock();
+ tty_unlock(tty);
mutex_lock(&tty_mutex);
- tty_lock();
+ tty_lock(tty);
spin_lock_irq(&current->sighand->siglock);
if (!noctty &&
current->signal->leader &&
@@ -2002,11 +2017,10 @@ retry_open:
tty->session == NULL)
__proc_set_tty(current, tty);
spin_unlock_irq(&current->sighand->siglock);
- tty_unlock();
+ tty_unlock(tty);
mutex_unlock(&tty_mutex);
return 0;
err_unlock:
- tty_unlock();
mutex_unlock(&tty_mutex);
/* after locks to avoid deadlock */
if (!IS_ERR_OR_NULL(driver))
@@ -2089,10 +2103,13 @@ out:
static int tty_fasync(int fd, struct file *filp, int on)
{
+ struct tty_struct *tty = file_tty(filp);
int retval;
- tty_lock();
+
+ tty_lock(tty);
retval = __tty_fasync(fd, filp, on);
- tty_unlock();
+ tty_unlock(tty);
+
return retval;
}
@@ -2929,6 +2946,7 @@ void initialize_tty_struct(struct tty_struct *tty,
tty->pgrp = NULL;
tty->overrun_time = jiffies;
tty_buffer_init(tty);
+ mutex_init(&tty->legacy_mutex);
mutex_init(&tty->termios_mutex);
mutex_init(&tty->ldisc_mutex);
init_waitqueue_head(&tty->write_wait);
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2024-12-22 18:17:07 +0000