[patch 19/87] Fix oops on close of hot-unplugged FTDI serial converter

Greg KH
2009-06-09T10:20:07Z

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2.6.29-stable review patch. If anyone has any objections, please let us know.

------------------

From: David Woodhouse <dwmw2@infradead.org>

commit 80193195f87ebca6d7417516d6edeb3969631c15 upstream.

Commit c45d6320 ("fix reference counting of ftdi_private") stopped
ftdi_sio_port_remove() from directly freeing the port-private data, with
the intention if the port was still open, it would be freed when
ftdi_close() is eventually called and releases the last refcount on the
structure.

That's all very well, but ftdi_sio_port_remove() still contains a call
to usb_set_serial_port_data(port, NULL) -- so by the time we get to
ftdi_close() for the port which was unplugged, it _still_ oopses on
dereferencing that NULL pointer, as it did before (and does in 2.6.29).

The fix is just not to clear the private data in ftdi_sio_port_remove().
Then the refcount is properly reduced to zero when the final kref_put()
happens in ftdi_close().

Remove a bogus comment too, while we're at it. And stop doing things
inside "if (priv)" -- it must _always_ be there.

Based loosely on an earlier patch by Daniel Mack, and suggestions by
Alan Stern.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Tested-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/usb/serial/ftdi_sio.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)

--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1485,14 +1485,7 @@ static int ftdi_sio_port_remove(struct u

remove_sysfs_attrs(port);

- /* all open ports are closed at this point
- * (by usbserial.c:__serial_close, which calls ftdi_close)
- */
-
- if (priv) {
- usb_set_serial_port_data(port, NULL);
- kref_put(&priv->kref, ftdi_sio_priv_release);
- }
+ kref_put(&priv->kref, ftdi_sio_priv_release);

return 0;
}