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Fri, 06 Dec 2019 15:11:46 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id xB6F9Z5Z191950; Fri, 6 Dec 2019 15:11:45 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3030.oracle.com with ESMTP id 2wqbeqxstc-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 06 Dec 2019 15:11:45 +0000 Received: from abhmp0003.oracle.com (abhmp0003.oracle.com [141.146.116.9]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id xB6FBhRZ023796; Fri, 6 Dec 2019 15:11:43 GMT Received: from bostrovs-us.us.oracle.com (/10.152.32.65) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 06 Dec 2019 07:11:43 -0800 Subject: Re: [PATCH] xen/pciback: Prevent NULL pointer dereference in quirks_show To: Stefan Nuernberger , linux-kernel@vger.kernel.org Cc: Juergen Gross , Ross Lagerwall , Uwe Dannowski , Conny Seidel , xen-devel@lists.xenproject.org, stable@vger.kernel.org References: <20191206134804.4537-1-snu@amazon.com> From: Boris Ostrovsky Autocrypt: addr=boris.ostrovsky@oracle.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20191206134804.4537-1-snu@amazon.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9462 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-1912060129 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9462 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-1912060129 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/6/19 8:48 AM, Stefan Nuernberger wrote: > From: Uwe Dannowski > > Reading /sys/bus/pci/drivers/pciback/quirks while unbinding can result > in dereferencing a NULL pointer. Instead, skip printing information > about the dangling quirk. > > Reported-by: Conny Seidel > Signed-off-by: Uwe Dannowski > Signed-off-by: Stefan Nuernberger > > Cc: xen-devel@lists.xenproject.org > Cc: stable@vger.kernel.org > --- > drivers/xen/xen-pciback/pci_stub.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c > index 097410a7cdb7..da725e474294 100644 > --- a/drivers/xen/xen-pciback/pci_stub.c > +++ b/drivers/xen/xen-pciback/pci_stub.c > @@ -1346,6 +1346,8 @@ static ssize_t quirks_show(struct device_driver *drv, char *buf) > quirk->devid.subdevice); > > dev_data = pci_get_drvdata(quirk->pdev); > + if (!dev_data) > + continue; > > list_for_each_entry(cfg_entry, &dev_data->config_fields, list) { Couldn't you have the same race here? -boris > field = cfg_entry->field;