Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753021AbcLLQDY (ORCPT ); Mon, 12 Dec 2016 11:03:24 -0500 Received: from mail-pf0-f196.google.com ([209.85.192.196]:36763 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752195AbcLLQDX (ORCPT ); Mon, 12 Dec 2016 11:03:23 -0500 Subject: Re: [V2] mtd: devices: docg3:- Handle return value of devm_ioremap. To: Boris Brezillon References: <1481511604-6116-1-git-send-email-arvind.yadav.cs@gmail.com> <20161212094218.2d29b34a@bbrezillon> Cc: robert.jarzmik@free.fr, dwmw2@infradead.org, computersforpeace@gmail.com, marek.vasut@gmail.com, richard@nod.at, cyrille.pitchen@atmel.com, linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org From: arvind Yadav Message-ID: <80fc935a-39aa-eaca-e75c-02078c3dab05@gmail.com> Date: Mon, 12 Dec 2016 21:33:05 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20161212094218.2d29b34a@bbrezillon> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2732 Lines: 74 There is problem, if you will use devm_ioremap_resource instead of devm_ioremap, than devm_ioremap_resource will call request_mem_region(). request_mem_region() allows to tell the kernel that this driver is going to use this range of I/O addresses, which will prevent other drivers to make an overlapping call to request_mem_region If other driver want to use same address space to access then it will not allow. Means we can not share same address space between two driver. Thanks -Arvind On Monday 12 December 2016 02:12 PM, Boris Brezillon wrote: > On Mon, 12 Dec 2016 08:30:04 +0530 > Arvind Yadav wrote: > >> Here, If devm_ioremap will fail. It will return NULL. >> Kernel can run into a NULL-pointer dereference. >> >> Signed-off-by: Arvind Yadav >> --- >> drivers/mtd/devices/docg3.c | 7 ++++++- >> 1 file changed, 6 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c >> index b833e6c..ffe3db0 100644 >> --- a/drivers/mtd/devices/docg3.c >> +++ b/drivers/mtd/devices/docg3.c >> @@ -2083,9 +2083,14 @@ static int __init docg3_probe(struct platform_device *pdev) >> dev_err(dev, "No I/O memory resource defined\n"); >> return ret; >> } >> - base = devm_ioremap(dev, ress->start, DOC_IOSPACE_SIZE); >> >> ret = -ENOMEM; >> + base = devm_ioremap(dev, ress->start, DOC_IOSPACE_SIZE); >> + if (!base) { >> + dev_err(dev, "failed to map I/O memory\n"); >> + return ret; >> + } >> + >> cascade = devm_kzalloc(dev, sizeof(*cascade) * DOC_MAX_NBFLOORS, >> GFP_KERNEL); >> if (!cascade) > How about going even further and doing the following? > This way you can drop the test on rres (it's done for you in > devm_ioremap_resource()), and you can directly return the error > returned by devm_ioremap_resource(). > > --->8--- > diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c > index b833e6cc684c..c59b91734344 100644 > --- a/drivers/mtd/devices/docg3.c > +++ b/drivers/mtd/devices/docg3.c > @@ -2077,13 +2077,10 @@ static int __init docg3_probe(struct > platform_device *pdev) int ret, floor; > struct docg3_cascade *cascade; > > - ret = -ENXIO; > ress = platform_get_resource(pdev, IORESOURCE_MEM, 0); > - if (!ress) { > - dev_err(dev, "No I/O memory resource defined\n"); > - return ret; > - } > - base = devm_ioremap(dev, ress->start, DOC_IOSPACE_SIZE); > + base = devm_ioremap_resource(dev, ress); > + if (IS_ERR(base)) > + return PTR_ERR(base); > > ret = -ENOMEM; > cascade = devm_kzalloc(dev, sizeof(*cascade) * DOC_MAX_NBFLOORS,