Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 52f6b5e1 authored by Benny Halevy's avatar Benny Halevy Committed by Greg Kroah-Hartman
Browse files

synchronization in usb_serial_put 



I think there is a race between usb_serial_put() and
usb_serial_get_by_index() (and get_free_serial()) with regards
to handling the serial port refcount.

usb_serial_get_by_index() gets a reference on the serial port under
table_lock while return_serial releases all the returned ports
from the table under the same lock.  However, the table_lock is not
taken around the call to kref_put, theoretically allowing to sneak
in and grab a reference after kref_put has already determined that
the reference count is zero (and before calling destroy_serial)
causing use after free.

Signed-off-by: default avatarBenny Halevy <bhalevy@ns1.bhalevy.com>
Cc: Oliver Neukum <oneukum@suse.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent efdff608

drivers/usb/serial/usb-serial.c

+2 −2
Original line number Diff line number Diff line
@@ -122,11 +122,9 @@ static void return_serial(struct usb_serial *serial) 
	if (serial == NULL)

		return;



	spin_lock(&table_lock);

	for (i = 0; i < serial->num_ports; ++i) {

		serial_table[serial->minor + i] = NULL;

	}

	spin_unlock(&table_lock);

}



static void destroy_serial(struct kref *kref)
@@ -174,7 +172,9 @@ static void destroy_serial(struct kref *kref) 


void usb_serial_put(struct usb_serial *serial)

{

	spin_lock(&table_lock);

	kref_put(&serial->kref, destroy_serial);

	spin_unlock(&table_lock);

}



/*****************************************************************************