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Commit a462067d authored by Anirudh Rayabharam's avatar Anirudh Rayabharam Committed by Greg Kroah-Hartman
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net: hso: fix null-ptr-deref during tty device unregistration 



commit 8a12f8836145ffe37e9c8733dce18c22fb668b66 upstream

Multiple ttys try to claim the same the minor number causing a double
unregistration of the same device. The first unregistration succeeds
but the next one results in a null-ptr-deref.

The get_free_serial_index() function returns an available minor number
but doesn't assign it immediately. The assignment is done by the caller
later. But before this assignment, calls to get_free_serial_index()
would return the same minor number.

Fix this by modifying get_free_serial_index to assign the minor number
immediately after one is found to be and rename it to obtain_minor()
to better reflect what it does. Similary, rename set_serial_by_index()
to release_minor() and modify it to free up the minor number of the
given hso_serial. Every obtain_minor() should have corresponding
release_minor() call.

Fixes: 72dc1c09 ("HSO: add option hso driver")
Reported-by: default avatar <syzbot+c49fe6089f295a05e6f8@syzkaller.appspotmail.com>
Tested-by: default avatar <syzbot+c49fe6089f295a05e6f8@syzkaller.appspotmail.com>
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarAnirudh Rayabharam <mail@anirudhrb.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
[sudip: adjust context]
Signed-off-by: default avatarSudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f8e8371c

drivers/net/usb/hso.c

+12 −21
Original line number Diff line number Diff line
@@ -635,7 +635,7 @@ static struct hso_serial *get_serial_by_index(unsigned index) 
	return serial;

}



static int get_free_serial_index(void)

static int obtain_minor(struct hso_serial *serial)

{

	int index;

	unsigned long flags;
@@ -643,8 +643,10 @@ static int get_free_serial_index(void) 
	spin_lock_irqsave(&serial_table_lock, flags);

	for (index = 0; index < HSO_SERIAL_TTY_MINORS; index++) {

		if (serial_table[index] == NULL) {

			serial_table[index] = serial->parent;

			serial->minor = index;

			spin_unlock_irqrestore(&serial_table_lock, flags);

			return index;

			return 0;

		}

	}

	spin_unlock_irqrestore(&serial_table_lock, flags);
@@ -653,15 +655,12 @@ static int get_free_serial_index(void) 
	return -1;

}



static void set_serial_by_index(unsigned index, struct hso_serial *serial)

static void release_minor(struct hso_serial *serial)

{

	unsigned long flags;



	spin_lock_irqsave(&serial_table_lock, flags);

	if (serial)

		serial_table[index] = serial->parent;

	else

		serial_table[index] = NULL;

	serial_table[serial->minor] = NULL;

	spin_unlock_irqrestore(&serial_table_lock, flags);

}
@@ -2249,6 +2248,7 @@ static int hso_stop_serial_device(struct hso_device *hso_dev) 
static void hso_serial_tty_unregister(struct hso_serial *serial)

{

	tty_unregister_device(tty_drv, serial->minor);

	release_minor(serial);

}



static void hso_serial_common_free(struct hso_serial *serial)
@@ -2273,25 +2273,23 @@ static int hso_serial_common_create(struct hso_serial *serial, int num_urbs, 
				    int rx_size, int tx_size)

{

	struct device *dev;

	int minor;

	int i;



	tty_port_init(&serial->port);



	minor = get_free_serial_index();

	if (minor < 0)

	if (obtain_minor(serial))

		goto exit2;



	/* register our minor number */

	serial->parent->dev = tty_port_register_device_attr(&serial->port,

			tty_drv, minor, &serial->parent->interface->dev,

			tty_drv, serial->minor, &serial->parent->interface->dev,

			serial->parent, hso_serial_dev_groups);

	if (IS_ERR(serial->parent->dev))

	if (IS_ERR(serial->parent->dev)) {

		release_minor(serial);

		goto exit2;

	}

	dev = serial->parent->dev;



	/* fill in specific data for later use */

	serial->minor = minor;

	serial->magic = HSO_SERIAL_MAGIC;

	spin_lock_init(&serial->serial_lock);

	serial->num_rx_urbs = num_urbs;
@@ -2692,9 +2690,6 @@ static struct hso_device *hso_create_bulk_serial_device( 


	serial->write_data = hso_std_serial_write_data;



	/* and record this serial */

	set_serial_by_index(serial->minor, serial);



	/* setup the proc dirs and files if needed */

	hso_log_port(hso_dev);
@@ -2751,9 +2746,6 @@ struct hso_device *hso_create_mux_serial_device(struct usb_interface *interface, 
	serial->shared_int->ref_count++;

	mutex_unlock(&serial->shared_int->shared_int_lock);



	/* and record this serial */

	set_serial_by_index(serial->minor, serial);



	/* setup the proc dirs and files if needed */

	hso_log_port(hso_dev);
@@ -3140,7 +3132,6 @@ static void hso_free_interface(struct usb_interface *interface) 
			cancel_work_sync(&serial_table[i]->async_get_intf);

			hso_serial_tty_unregister(serial);

			kref_put(&serial_table[i]->ref, hso_serial_ref_free);

			set_serial_by_index(i, NULL);

		}

	}