[PATCH 068/149] synchronization in usb_serial_put
Greg Kroah-Hartman <[email protected]>
| Newsgroups | gmane.linux.usb.devel |
|---|---|
| Message-ID | <[email protected]> |
From: Benny Halevy <[email protected]> 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: Benny Halevy <[email protected]> Cc: Oliver Neukum <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/usb/serial/usb-serial.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c index e3e3728..a366565 100644 --- a/drivers/usb/serial/usb-serial.c +++ b/drivers/usb/serial/usb-serial.c @@ -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); } /***************************************************************************** -- 1.5.2.2 ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel