From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:52444 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752963AbdK1MMo (ORCPT ); Tue, 28 Nov 2017 07:12:44 -0500 Date: Tue, 28 Nov 2017 12:13:12 +0000 From: Lorenzo Pieralisi To: David Laight Cc: 'Niklas Cassel' , Kishon Vijay Abraham I , Bjorn Helgaas , Niklas Cassel , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v3 3/3] PCI: endpoint: Fix find_first_zero_bit() usage Message-ID: <20171128121312.GA15106@red-moon> References: <20171127154955.22214-1-niklas.cassel@axis.com> <20171127154955.22214-4-niklas.cassel@axis.com> <227791f09ccd4aa8972ba334fd948f4e@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <227791f09ccd4aa8972ba334fd948f4e@AcuMS.aculab.com> Sender: linux-pci-owner@vger.kernel.org List-ID: On Tue, Nov 28, 2017 at 09:53:12AM +0000, David Laight wrote: > From: Niklas Cassel > > Sent: 27 November 2017 15:50 > > find_first_zero_bit()'s parameter 'size' is defined in bits, > > not in bytes. > > > > Calling find_first_zero_bit() with the wrong size unit > > will lead to insidious bugs. > > > > Fix this by calling find_first_zero_bit() with size > > BITS_PER_LONG, rather than sizeof(). > > > > Also add proper error handling for find_first_zero_bit(), > > since this was missing. > > > > Fixes: d74679911610 ("PCI: endpoint: Introduce configfs entry for configuring EP functions") > > Signed-off-by: Niklas Cassel > > --- > > drivers/pci/endpoint/pci-ep-cfs.c | 8 +++++++- > > 1 file changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/pci/endpoint/pci-ep-cfs.c b/drivers/pci/endpoint/pci-ep-cfs.c > > index e1f5adc9e113..0a22a7976580 100644 > > --- a/drivers/pci/endpoint/pci-ep-cfs.c > > +++ b/drivers/pci/endpoint/pci-ep-cfs.c > > @@ -109,7 +109,12 @@ static int pci_epc_epf_link(struct config_item *epc_item, > > return ret; > > > > func_no = find_first_zero_bit(&epc_group->function_num_map, > > - sizeof(epc_group->function_num_map)); > > + BITS_PER_LONG); > > Surely this should be either 8 * sizeof() or you should use ffz() > that takes a numeric argument rather than the function designed > for arbitrary size bitmaps. Do you see a problem with this code ? It can be made a bitmap by allocating it using epc->max_functions as bitmap number of bits and that can be made on top of the code above that would go in as a fix unless you strongly object to it, as Joe mentioned both ffz+| and find_first_zero_bit()+set_bit() are ok with me as long as we choose one and fix the issue. Thanks, Lorenzo