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Fix oops on close of hot-unplugged FTDI serial converter 

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>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Woodhouse 2009-05-18 13:07:35 +01:00 committed by Linus Torvalds
parent dbf8c11f82
commit 80193195f8
1 changed files with 1 additions and 8 deletions
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9
drivers/usb/serial/ftdi_sio.c
View File

@ -1487,14 +1487,7 @@ static int ftdi_sio_port_remove(struct usb_serial_port *port)
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;
}