Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 31 Mar 2022 08:41:56 +0300
From:   Dan Carpenter <dan.carpenter@oracle.com>
To:     Wenchao Hao <haowenchao@huawei.com>
Cc:     fmdefrancesco@gmail.com, axboe@kernel.dk, jejb@linux.ibm.com,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-scsi@vger.kernel.org, martin.petersen@oracle.com,
        syzbot+f08c77040fa163a75a46@syzkaller.appspotmail.com,
        syzkaller-bugs@googlegroups.com, linfeilong@huawei.com
Subject: Re: [PATCH] scsi: sd: call device_del() if device_add_disk() fails
Message-ID: <20220331054156.GI3293@kadam>
References: <20220329154948.10350-1-fmdefrancesco@gmail.com>
 <20220331152622.616534-1-haowenchao@huawei.com>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220331152622.616534-1-haowenchao@huawei.com>
User-Agent: Mutt/1.9.4 (2018-02-28)
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?ivJWDhGNii+Pp2nxbKMu1RoN9bDJgN+HqtdvStLg48h1LwhwiSOfO81q6I3R?=
 =?us-ascii?Q?RLCHYnES7zDB1e4Kk+QJMcEBWXZlHWRzQfN5Clmtn1P/aV7VwNiZtih661TU?=
 =?us-ascii?Q?DDp6Ln6P0ATqgGK0T0Q/y4Ik6IvKegn51qOTsW9tieRye/vCaJA5HnPAv9dY?=
 =?us-ascii?Q?U8YG44CFs5oDsSuBk0jTMrwVDKHFKn4z8CfaeIHJEPl6oMtf8R8O2aTA9ohv?=
 =?us-ascii?Q?2gTsOfO8FJ7X3oaoKtCS/0kpQqfeMEGXBQmdaVvS6DZzPEb3RYYakTo4Gpo1?=
 =?us-ascii?Q?CUDmMAP/QnBmPHmdzSUO0pezSbBN4Jpdvp/F8uAqRQUZqM6ZolROVr1NLsM8?=
 =?us-ascii?Q?tUOiPIBtlynVqeoc4pzCtpaZDlbgX8KK1nLuN4YmOumwsv8hbcsz4ojdde+n?=
 =?us-ascii?Q?MutEMgNMpw+Xtbppqc/g2tCoFWW/4lGH/QrnSkGoagwbODzUFdABlbGxLrmK?=
 =?us-ascii?Q?fkD+ZZX5Yp8M2XS9C7P8fmoc7wnH+DNrp6Ru1Az9tCnQtaJ4QWwLvkcgtgzQ?=
 =?us-ascii?Q?nQHLuvr2FUJxyDZ3EEgWILhIVP3sBDLDMH35Ngm+aI39EsrrBfI9CIfMFsC2?=
 =?us-ascii?Q?FqbqvcVlVGU62CqA2B5Yqq3ZKBVT6ChrtP534HouqFv+G6Rcasz43Q6Qqh53?=
 =?us-ascii?Q?TdE9t4LE1ePwXaTF7NzRAWieLxOJjdgDE7GPWoAWOpgn9NiL0phukXiU4jKK?=
 =?us-ascii?Q?6/EhQp97P3X4czxWcQWXCQk0j3GCh+7xjXf54VwZRN0a/V4YVcg/uzGCK1Hi?=
 =?us-ascii?Q?DPGjquNmnjnmNlaGxeNPTx4JmPszNs1cYVGV2hz+jmLuA+OZbClwMJBUjVmY?=
 =?us-ascii?Q?Nu1KNVOH1fnRQoYMe7YdVn8pA1dM/KWhHeIR+TP0xXx+/GWLzPMZf8dHAlA0?=
 =?us-ascii?Q?kK2cZPtpRRk7yPfZGQkviFLgQwCCvXoY8WaDjKhbCobA8U13C3Zom04mpOMd?=
 =?us-ascii?Q?dTEwBZDGhvVFdrQFjZxkS3XIkVlDr9Rqee9gTQuYcinkUEtWaa37lE2CZm8i?=
 =?us-ascii?Q?AESEUlH09dzK8t+IY61tAQKAOCnc+m+BlkNJyjyqcmaCbYOu1MYoeXthLr6O?=
 =?us-ascii?Q?fzDx78Yr4/uR++OEKjAAfUJ/xNxye8GEQRppMWK1H2b+ksrrBajWI+85yxmN?=
 =?us-ascii?Q?Rod0UcnaMslbMsimF/RCFm/iYIiLke09A/Ji4rCDGLIOGvnh6Sg5G1dNL43a?=
 =?us-ascii?Q?SABKYklfApnYNuSN564V62+BB+F37uXbTPuKxB6NHNfQVj/a+VQ7mNF5WT2C?=
 =?us-ascii?Q?V932OySKx8x5Yz9q6RWpGvPqCZIfWc5ozQKRXVAHO1C7/2CoxGZca5kQkbU7?=
 =?us-ascii?Q?MiBrFrWb8qr6B4ajNLfzqLhM3YeY5fK6fx9814sFn7RsOYzDubNHoH7c9rRO?=
 =?us-ascii?Q?jEhMg/WdBgcDg4dAkA7MqkMPjXVKW1mf415Zpl+e2bSR3/aA4F+NhEqH+Xpy?=
 =?us-ascii?Q?PE6HiqvBS70v+Rr+yBhn8M0fnAMf2khvrT+j7iuvGlkH6Fa41/8FK0wElLMj?=
 =?us-ascii?Q?cMVlBYR1UAC1UvDdNSavYZpPe4BTMuXPUCFCWR5dDVeoydtqdjZ9z4QDWohm?=
 =?us-ascii?Q?NBByJuzLsJsgh1WOC/yFQigs3KbnM5BfS0lJRYozCUf7LI3cNOZR8UMj+8Wk?=
 =?us-ascii?Q?2n7ic9DDPNcOxRZ1pvNIzrk3/Fb/l7Jg8oqsljUsDcAWl0DXMv18g4PO6Fum?=
 =?us-ascii?Q?FxEA3b9s1Rwz2v4BffDQe8ACKDD/XJm50Y7IOHgf1FuhKx3hUz+I1fvcwZd/?=
 =?us-ascii?Q?2T+NzDOsLfRUwHkRdW9h71hOAFyoMsA=3D?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 5191c8e2-d959-4964-b15a-08da12d93f97
X-MS-Exchange-CrossTenant-AuthSource: MWHPR1001MB2365.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 31 Mar 2022 05:42:31.2955
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: glNOEUNLHMAW1CE0mkipJKWz35FDdKbxKOrnLPhU+vbtSBAWBgenhRUzcFviLcHQDN/B2UaZjAbGXaXUsA74Oq43/m7fjkHHF3LtP1dWCps=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR10MB3253
X-Proofpoint-Virus-Version: vendor=nai engine=6300 definitions=10302 signatures=695566
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 malwarescore=0 spamscore=0
 phishscore=0 adultscore=0 mlxlogscore=999 suspectscore=0 bulkscore=0
 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000
 definitions=main-2203310032
X-Proofpoint-ORIG-GUID: mlVrc2CQE3mbsfsXQAQL-9oVyoaNTPtV
X-Proofpoint-GUID: mlVrc2CQE3mbsfsXQAQL-9oVyoaNTPtV
X-Spam-Status: No, score=-2.8 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW,
        RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE,
        T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, Mar 31, 2022 at 11:26:22AM -0400, 'Wenchao Hao' via syzkaller-bugs wrote:
> I do not think it's necessary to call device_del() on this path. If the device
> has been added, put_device() would delete it from sysfs. So the origin error
> handle is ok with me.
> 

No.  The original is buggy and it was detected at runtime by syzbot.
It's not static analysis, it is an actual bug found in testing.

The device_put() unwinds device_initialize().  The device_del() unwinds
device_add().  Take a look at the comments to device_add() or take a
look at how device_register/unregister() work.

The temptation was to call device_unregister() which is a combined
device_del(); device_put(); but when the device_initialize() and
device_add() are called separately, then I think it is more readable to
call del and put separately as well.

regards,
dan carpenter