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synchronization in usb_serial_put

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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 <bhalevy@ns1.bhalevy.com>
Cc: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Benny Halevy
2007-05-15 11:15:27 +03:00
committed by Greg Kroah-Hartman
parent efdff60885
commit 52f6b5e1f1
1 changed files with 2 additions and 2 deletions
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4
drivers/usb/serial/usb-serial.c
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@@ -122,11 +122,9 @@ static void return_serial(struct usb_serial *serial)
if (serial == NULL) if (serial == NULL)
return; return;
spin_lock(&table_lock);
for (i = 0; i < serial->num_ports; ++i) { for (i = 0; i < serial->num_ports; ++i) {
serial_table[serial->minor + i] = NULL; serial_table[serial->minor + i] = NULL;
} }
spin_unlock(&table_lock);
} }
static void destroy_serial(struct kref *kref) 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) void usb_serial_put(struct usb_serial *serial)
{ {
spin_lock(&table_lock);
kref_put(&serial->kref, destroy_serial); kref_put(&serial->kref, destroy_serial);
spin_unlock(&table_lock);
} }
/***************************************************************************** /*****************************************************************************