Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753614Ab0BIWwx (ORCPT ); Tue, 9 Feb 2010 17:52:53 -0500 Received: from mga10.intel.com ([192.55.52.92]:20515 "EHLO fmsmga102.fm.intel.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752566Ab0BIWww (ORCPT ); Tue, 9 Feb 2010 17:52:52 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.49,439,1262592000"; d="scan'208";a="539317407" Date: Tue, 9 Feb 2010 14:52:50 -0800 From: Sarah Sharp To: Roel Kluin Cc: Alan Stern , Greg Kroah-Hartman , linux-usb@vger.kernel.org, Andrew Morton , LKML Subject: Re: [PATCH] USB: don't read past config->interface[] if usb_control_msg() fails in usb_reset_configuration() Message-ID: <20100209225250.GA5182@xanatos> References: <4B7186F1.808@gmail.com> <4B71DB34.5090708@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4B71DB34.5090708@gmail.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1926 Lines: 48 On Tue, Feb 09, 2010 at 11:01:24PM +0100, Roel Kluin wrote: > After the loop `for (i = 0; i < config->desc.bNumInterfaces; i++)' if no > break occurred, i equals config->desc.bNumInterfaces. so if > usb_control_msg() failed then after goto reset_old_alts we read from > config->interface[config->desc.bNumInterfaces]. > > Reported-by: "Juha Leppanen" > Signed-off-by: Roel Kluin > --- > > >> You correctly identified a problem, but your fix is wrong -- or at > >> least, it is much too complicated. The proper fix goes like this: > > > > /* If not, reinstate the old alternate settings */ > > if (retval < 0) { > > reset_old_alts: > > - for (; i >= 0; i--) { > > + for (i--; i >= 0; i--) { > > struct usb_interface *intf = config->interface[i]; > > struct usb_host_interface *alt; > > > Are you really sure this is better? Yes. > If usb_hcd_alloc_bandwidth() fails, in the loop _before_ the > reset_old_alts label, don't we still have to reinstate the old > alternate settings for that usb_interface config->interface[i]? This > was what my initial patch tried to do. No, you do not. Take a look at usb_hcd_alloc_bandwidth() in drivers/usb/core/hcd.c. If an allocation fails for interface i when the HCD's check_bandwidth() function is called, then hcd->driver->reset_bandwidth is called. We only need to clean up the interfaces that have successfully been allocated bandwidth (0 to i - 1). > Alternatively usb_hcd_alloc_bandwidth() could undo what it does if an > error occurs there, then I think i could be decremented. Yes, that's what usb_hcd_alloc_bandwidth() does at the reset label. Sarah -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/