Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) client-ip=2620:137:e000::3:7;
Message-ID: <9842e1cc-3e61-3759-30f0-b4968622e0a7@intel.com>
Date:   Thu, 28 Sep 2023 08:45:11 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Firefox/102.0 Thunderbird/102.15.1
Subject: Re: [PATCH RESEND] fpga: region: Fix possible memory leak in
 fpga_region_register_full()
Content-Language: en-US
To:     Jinjie Ruan <ruanjinjie@huawei.com>, <mdf@kernel.org>,
        <hao.wu@intel.com>, <yilun.xu@intel.com>, <trix@redhat.com>,
        <linux-fpga@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <20230928091636.1209914-1-ruanjinjie@huawei.com>
From:   Russ Weight <russell.h.weight@intel.com>
In-Reply-To: <20230928091636.1209914-1-ruanjinjie@huawei.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?OHdyR09NNmluSlRmdEE2TkdxbitsdzJGM1hpUDZrQWVrQU1lWDExQ0N2RDhm?=
 =?utf-8?B?VUkyTmQ5RlJLUVR1YUIzWW1iZlVRaTB6UE50RFg4ZWRHYnExQkJwekFDdUM5?=
 =?utf-8?B?VExHVmdvRlVUcEo5UnMxZlBOd1J5cGtRdXVodHRlZmZMRGl0aHF0cXpGeXZi?=
 =?utf-8?B?NUhWeDJXTkNGa3BsQnlndEZkaVIxcEdUVkJhYzN3VGROUlhFTlhZNGNHVVE5?=
 =?utf-8?B?bis5UVhVUm9yTm9HNmdrWUpWcGNsWjdVT29WaGN1ZTA3eExHbW9SdkFyT1Bs?=
 =?utf-8?B?WGtWZXM4T2dNOGttOTh3QnhRVjc2V3NuWnkwYzlSQzh6ekttTGdDSFNsQTlO?=
 =?utf-8?B?aXNKcWZTU3VFck1MSmpBZDFUVzRoWlZmaHJ4NTB2eUlKSkdXRDBDMy8reGxD?=
 =?utf-8?B?ODFVeFpRaFVEQzJnZXFWcTNhM0FqaWV4RkFrVjhiMWZZTmhPYlp3VkxYaW1j?=
 =?utf-8?B?V1h3V0U5K00xRjdCN1VsRzdzcDQ1eVJ2SGZGU000cWVRQkpJdS9mdFJWRU5U?=
 =?utf-8?B?Qm56MDNaZGxtM0F6Z3F0SHFFU01hQXF1VGVKVk5zaUJSelpZRXloYXlkNk9Y?=
 =?utf-8?B?Rzc2SEFoRGtjMnJndEJzYjlBaFVFWlZseml2NUplZi9XdVplVCt1UmlzTTQ5?=
 =?utf-8?B?dXhlTm5DVmRUY3pHUGJZbGxYNjJOZHNOYTlyUGVxMkxCZGxKOE5CT25SKzMw?=
 =?utf-8?B?UG44QWE0bzFPVkFEcFZrNHNwWnFrZkc1RHVyTTQxc1BLOWlCTHBnMVhIOFVH?=
 =?utf-8?B?VEdmMG1vbTVwNlZPTGt5QWVUbGpuOXJEWFlac1BENFhscWE2ZkxCSjRvenpq?=
 =?utf-8?B?cDBqVG9OTWtERE92UE1weFE4aG40ajdhS2h0VVIyZlkwNWo3MTlIaFNabXU1?=
 =?utf-8?B?M2RlNWFMVngvQ29aS3F6UElxUmJxak1aNGx0V05yaHhzWEdKc3lhR3JJbFBT?=
 =?utf-8?B?aENBaUVlWmZLTm9aTEZTOUpKdnFFWU5tWXFuSUNiNUNkenFkZ3BPWFFQalpt?=
 =?utf-8?B?RUo5M2hhWmhYTHdMMTBJREhKZTJVRVE5S291L3BLUiswcE0zVUtCTkExaEF1?=
 =?utf-8?B?Rklad3dlQ25iYTg4bEtGYmdKMkxCdjh2UTd0Zjk3ZkZMVHllNEpqdC8wcUFU?=
 =?utf-8?B?WmxhRFAwWlhUS1JUZCs3TlpvTnc2VVlqcEJPWmZoVHoxUUJkeGdPdU5MRWlv?=
 =?utf-8?B?NkVzTWhmdWxYd1BjWDVVV3Awb0hRYUpTQVFsNExTQU5uajVpSEdhSkxTd25T?=
 =?utf-8?B?R2J5TjFzT3FSYzVwbmxaV3hiZ2dBOXZjTXRwdjU4VW5PbGF1a1NTQ003aGxr?=
 =?utf-8?B?RS95MTZHUysxNzhrdXMvck5vVkJ3b2s4OFhseWRyS0ZHd0cvUGRaZmhHN2ZH?=
 =?utf-8?B?U2o2YlkvNUFYaGZ6RkVVei8yc1J1eXltT2VaakNrZTFvOHVNWTR1K0ZOU1FQ?=
 =?utf-8?B?WkMyVXdZV05qcncwSFFHaFZPNzF2aFN1bERSQU9KSWV5US94WFRZVzhIZmQ3?=
 =?utf-8?B?UkRJT3RhNnhCMUJ6TjFOSjRJWDMwNDRXRWk0N2lxYUlwVDByc2hIQ1N2NklQ?=
 =?utf-8?B?UUFqZ0kyZTA4ZUxPam03aHVEMHo3NnN6b0k2eXpybTBXK1pPckNXTXdzcytz?=
 =?utf-8?B?dUlkQnRKZDBEQVVYTlFic2pFL3FIQUdWUGhZeG5IU3M4S0lJWnppajNyK1FJ?=
 =?utf-8?B?dVRtejVlaXZHR1NHNU9yWjlWZ3VkYTloM3F2cHhKK2NnT29nc0gwTTlURkVl?=
 =?utf-8?B?S1JJdEFGQktrNUhyemRCZnQvbXVHbUV5Z3ZFTXlxNXRDM1NscUgxZUJlM3Iv?=
 =?utf-8?B?RSs2cDdQVktwYml1Q0I2d1A2T2NWSUgrRlpudnJDQ1dRZVFLV204bjVxVWlh?=
 =?utf-8?B?ZHNaR1RGZEpIaWJMaHJBUys2Sk5MYWFFTFA4bzJWU083ZzY4VmZ6QWtFak9w?=
 =?utf-8?B?UEQwWWJHK05TK28rQkg0RmpIZG8wZ0ZiVWYzV3kwclFJeVQyK1JldDREamwz?=
 =?utf-8?B?S0Nmd3lTOFZRdm5KeXg0NE9JSzIwWUZXdU5ETEw1aVNNaEs4VE9kSFhjSCsv?=
 =?utf-8?B?Rzc1a2JyQkh4Z3ZWa0kxY08rdk1EREpNN0VQV3hVR0NlQm1nSGdJc24wZHRD?=
 =?utf-8?B?b1NEUXBTSXNhZHpRalZXdHF3N0lxZUZrV3dtK0hsb0diaU53NlZDQjVWY3NN?=
 =?utf-8?B?TVE9PQ==?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 16516a39-3f47-4bf4-d2b3-08dbc039e78f
X-MS-Exchange-CrossTenant-AuthSource: MW4PR11MB6763.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Sep 2023 15:45:13.4908
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: IPmkfTYLgXBY2DuENXqeBFy7rUfWCarYlewjLBbJyQ2v0RHVKfxJ+D/t4cSNGFRMaX/eTAUGQbZ2TGrmIc95Mfc+wEXYw5HwZqWmPF2FTfY=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH8PR11MB7095
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-3.6 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,
        RCVD_IN_DNSWL_BLOCKED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,
        SPF_HELO_NONE,SPF_NONE 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
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (snail.vger.email [0.0.0.0]); Thu, 28 Sep 2023 08:45:45 -0700 (PDT)


On 9/28/23 02:16, Jinjie Ruan wrote:
> If device_register() fails in fpga_region_register_full(), the region
> allocated by kzalloc() and the id allocated by ida_alloc() also need be
> freed otherwise will cause memory leak.
>
> Fixes: 8886a579744f ("fpga: region: Use standard dev_release for class driver")
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
>  drivers/fpga/fpga-region.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/fpga/fpga-region.c b/drivers/fpga/fpga-region.c
> index b364a929425c..9dc6314976ef 100644
> --- a/drivers/fpga/fpga-region.c
> +++ b/drivers/fpga/fpga-region.c
> @@ -228,12 +228,13 @@ fpga_region_register_full(struct device *parent, const struct fpga_region_info *
>  
>  	ret = device_register(&region->dev);

The comments for device_register() say:

 * NOTE: _Never_ directly free @dev after calling this function, even
 * if it returned an error! Always use put_device() to give up the
 * reference initialized in this function instead.

Note that dev is embedded in the region structure, so freeing region
means freeing dev.

The expectation is that after device_register() has been called, even
if it returns an error, put_device() is used to lower the reference
count. When the reference count is zero, the fpga_region_dev_release()
function is called. fpga_region_dev_release() frees calls ida_free()
and frees the region.

Have you observed different behavior? Do you have evidence of a memory
leak?

Thanks,
- Russ

>  	if (ret) {
> -		put_device(&region->dev);
> -		return ERR_PTR(ret);
> +		goto err_put_device;
>  	}
>  
>  	return region;
>  
> +err_put_device:
> +	put_device(&region->dev);
>  err_remove:
>  	ida_free(&fpga_region_ida, id);
>  err_free: