Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758208AbaLKSmB (ORCPT ); Thu, 11 Dec 2014 13:42:01 -0500 Received: from mail-qa0-f50.google.com ([209.85.216.50]:42985 "EHLO mail-qa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754966AbaLKSl7 (ORCPT ); Thu, 11 Dec 2014 13:41:59 -0500 MIME-Version: 1.0 In-Reply-To: <2128690.c90ERDd9ZP@xps13> References: <31518562.V5Oyo0POsI@xps13> <20141211085801.GR1300@lahna.fi.intel.com> <20141211140307.GE1300@lahna.fi.intel.com> <2128690.c90ERDd9ZP@xps13> Date: Thu, 11 Dec 2014 13:41:57 -0500 Message-ID: Subject: Re: NULL pointer dereference in i2c-hid From: Benjamin Tissoires To: Gabriele Mazzotta Cc: Mika Westerberg , linux-input , "linux-kernel@vger.kernel.org" , Benjamin Tissoires , Andrew Duggan , Jiri Kosina Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 11, 2014 at 1:16 PM, Gabriele Mazzotta wrote: > On Thursday 11 December 2014 16:03:07 Mika Westerberg wrote: >> On Thu, Dec 11, 2014 at 10:58:01AM +0200, Mika Westerberg wrote: >> > On Wed, Dec 10, 2014 at 06:04:51PM +0100, Gabriele Mazzotta wrote: >> > > my laptop uses a touchpad that needs hid-rmi along with i2c-hid to work. >> > > i2c-hid and hid-rmi can be loaded and unloaded independelty from each >> > > other, however since 34f439e4afcd ("HID: i2c-hid: add runtime PM support") >> > > if I unload hid-rmi and after it I also unload i2c-hid, I get a NULL >> > > pointer dereference. >> > >> > I'll look into this. >> > >> > I can reproduce this easily with i2c-hid + hid-multitouch following your >> > directions. >> >> Can you try the below patch? >> >> I think we shouldn't free buffers yet in ->stop() because we need the >> command buffer sending power commands to the device. Also it seems that >> ->start() re-allocates buffers anyway if maximum size increases. >> >> It shouldn't even leak memory as we release buffers at ->remove() >> anyway. >> >> diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c >> index 62cec01937ea..68a8c938feea 100644 >> --- a/drivers/hid/i2c-hid/i2c-hid.c >> +++ b/drivers/hid/i2c-hid/i2c-hid.c >> @@ -705,12 +705,7 @@ static int i2c_hid_start(struct hid_device *hid) >> >> static void i2c_hid_stop(struct hid_device *hid) >> { >> - struct i2c_client *client = hid->driver_data; >> - struct i2c_hid *ihid = i2c_get_clientdata(client); >> - >> hid->claimed = 0; >> - >> - i2c_hid_free_buffers(ihid); >> } >> >> static int i2c_hid_open(struct hid_device *hid) Mika, you can add my Rev-by when submitting this patch to the mailing list. > > Yes, it works, thanks. > > This change seems to also prevent kernel ooops when I unload either > i2c-hid or i2c-designware-platform while the touchpad is in use, > thing that is likely to happen because of the other bug I reported. > > Speaking of it, does any of you have any suggestion on how to debug it? Hehe, I coincidentally just replied to your bug with one patch to try (that was proposed by the intel folks back in May[1]). The powertop problem is IMO really worrying because the purpose of i2c_hid was to reduce power consumption :) Anyway, thanks for the quick test. Cheers, Benjamin [1] https://patchwork.kernel.org/patch/4133771/ -- 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/