Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752021Ab3HUJZX (ORCPT ); Wed, 21 Aug 2013 05:25:23 -0400 Received: from shrek-wifi.podlesie.net ([93.179.225.50]:60836 "EHLO shrek.podlesie.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751976Ab3HUJZU (ORCPT ); Wed, 21 Aug 2013 05:25:20 -0400 Date: Wed, 21 Aug 2013 11:25:16 +0200 From: Krzysztof Mazur To: Alan Stern Cc: linux-usb@vger.kernel.org, Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Daniel J Blueman Subject: Re: [PATCH 2/2] usb: fail on usb_hub_create_port_device() errors Message-ID: <20130821092515.GA3685@shrek.podlesie.net> References: <20130820190730.GA13696@shrek.podlesie.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4280 Lines: 114 On Tue, Aug 20, 2013 at 03:50:37PM -0400, Alan Stern wrote: > On Tue, 20 Aug 2013, Krzysztof Mazur wrote: > > > On Tue, Aug 20, 2013 at 02:18:57PM -0400, Alan Stern wrote: > > > On Tue, 20 Aug 2013, Krzysztof Mazur wrote: > > > > > > > Ignoring usb_hub_create_port_device() errors cause later NULL pointer > > > > deference when uninitialized hub->ports[i] entries are dereferenced > > > > after port memory allocation error. > > > > > > > > Signed-off-by: Krzysztof Mazur > > > > --- > > > > I'm not sure if failing in that case is a good idea, but other solutions > > > > are more complex. > > > > > > > > I tried also changing hdev->maxchild and skiping initialization > > > > of later ports, but it didn't work because in some cases > > > > hub->descriptor->bNbrPorts is used instead of hdev->maxchild. > > > > With simulated usb_hub_create_port_device() failure I have an Oops > > > > in hub_power_on(). > > > > > > I think this patch is correct. However, we also should change the > > > other places that refer to bNbrPorts; make them use maxchild instead. > > > > Ok, I can try to catch all such cases and fix problems with > > maxchild < bNBrPorts, but I think that changing bNBrPorts to maxchild > > might be not enough. For instance: > > We should never have maxchild < bNbrPorts (unless maxchild is 0). But > just in case we do, changing the code is a good idea. > > Besides, "hub->maxchild" is shorter and easier to read than > "hub->descriptor->bNbrPorts". :-) > It's "hub->hdev->maxchild", but it's still shorter and in many places it's just "hdev->maxchild" :) I tested that with maxchild < bNbrPorts and there are no NULL pointer dereferences anymore. Krzysiek -- >8 -- Subject: [PATCH 3/2] usb: don't use bNbrPorts after initialization After successful initialization hub->descriptor->bNbrPorts and hub->hdev->maxchild are equal, but using hub->hdev->maxchild is preferred because that value is explicitly used for initialization of hub->ports[]. Signed-off-by: Krzysztof Mazur --- drivers/usb/core/hub.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 292ffa8..86e353f 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -451,7 +451,7 @@ static void led_work (struct work_struct *work) if (hdev->state != USB_STATE_CONFIGURED || hub->quiescing) return; - for (i = 0; i < hub->descriptor->bNbrPorts; i++) { + for (i = 0; i < hdev->maxchild; i++) { unsigned selector, mode; /* 30%-50% duty cycle */ @@ -500,7 +500,7 @@ static void led_work (struct work_struct *work) } if (!changed && blinkenlights) { cursor++; - cursor %= hub->descriptor->bNbrPorts; + cursor %= hdev->maxchild; set_port_led(hub, cursor + 1, HUB_LED_GREEN); hub->indicator[cursor] = INDICATOR_CYCLE; changed++; @@ -826,7 +826,7 @@ static unsigned hub_power_on(struct usb_hub *hub, bool do_delay) else dev_dbg(hub->intfdev, "trying to enable port power on " "non-switchable hub\n"); - for (port1 = 1; port1 <= hub->descriptor->bNbrPorts; port1++) + for (port1 = 1; port1 <= hub->hdev->maxchild; port1++) if (hub->ports[port1 - 1]->power_is_on) set_port_feature(hub->hdev, port1, USB_PORT_FEAT_POWER); else @@ -4655,9 +4655,7 @@ static void hub_events(void) hub_dev = hub->intfdev; intf = to_usb_interface(hub_dev); dev_dbg(hub_dev, "state %d ports %d chg %04x evt %04x\n", - hdev->state, hub->descriptor - ? hub->descriptor->bNbrPorts - : 0, + hdev->state, hdev->maxchild, /* NOTE: expects max 15 ports... */ (u16) hub->change_bits[0], (u16) hub->event_bits[0]); @@ -4702,7 +4700,7 @@ static void hub_events(void) } /* deal with port status changes */ - for (i = 1; i <= hub->descriptor->bNbrPorts; i++) { + for (i = 1; i <= hdev->maxchild; i++) { if (test_bit(i, hub->busy_bits)) continue; connect_change = test_bit(i, hub->change_bits); -- 1.8.4.rc4.527.g303b16c -- 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/