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Received: from DM6PR12MB3370.namprd12.prod.outlook.com (2603:10b6:5:38::25) by BL1PR12MB5175.namprd12.prod.outlook.com (2603:10b6:208:318::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5723.30; Fri, 21 Oct 2022 08:24:40 +0000 Received: from DM6PR12MB3370.namprd12.prod.outlook.com ([fe80::d309:77d2:93d8:2425]) by DM6PR12MB3370.namprd12.prod.outlook.com ([fe80::d309:77d2:93d8:2425%7]) with mapi id 15.20.5723.035; Fri, 21 Oct 2022 08:24:40 +0000 Message-ID: <35e66c7c-ff25-efd3-cfbc-d06130687aa7@amd.com> Date: Fri, 21 Oct 2022 04:24:37 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.3 Subject: Re: [PATCH 00/11] fix memory leak while kset_register() fails Content-Language: en-CA To: Greg KH Cc: Yang Yingliang , linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, linux-f2fs-devel@lists.sourceforge.net, linux-erofs@lists.ozlabs.org, ocfs2-devel@oss.oracle.com, linux-mtd@lists.infradead.org, amd-gfx@lists.freedesktop.org, rafael@kernel.org, somlo@cmu.edu, mst@redhat.com, jaegeuk@kernel.org, chao@kernel.org, hsiangkao@linux.alibaba.com, huangjianan@oppo.com, mark@fasheh.com, jlbec@evilplan.org, joseph.qi@linux.alibaba.com, akpm@linux-foundation.org, alexander.deucher@amd.com, richard@nod.at, liushixin2@huawei.com References: <20221021022102.2231464-1-yangyingliang@huawei.com> <5efd73b0-d634-d34f-3d7a-13d674e40d04@amd.com> From: Luben Tuikov In-Reply-To: Content-Type: text/plain; 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envelope-from=Luben.Tuikov@amd.com; helo=NAM12-MW2-obe.outbound.protection.outlook.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Fri, 21 Oct 2022 09:01:22 -0400 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2022-10-21 04:18, Greg KH wrote: > On Fri, Oct 21, 2022 at 03:55:18AM -0400, Luben Tuikov wrote: >> On 2022-10-21 01:37, Greg KH wrote: >>> On Fri, Oct 21, 2022 at 01:29:31AM -0400, Luben Tuikov wrote: >>>> On 2022-10-20 22:20, Yang Yingliang wrote: >>>>> The previous discussion link: >>>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Flkml%2F0db486eb-6927-927e-3629-958f8f211194%40huawei.com%2FT%2F&data=05%7C01%7Cluben.tuikov%40amd.com%7Cd41da3fd6449492d01f808dab33cdb75%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638019371236833115%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=C%2Bj1THkHpzVGks5eqB%2Fm%2FPAkMRohR7CYvRnOCqUqdcM%3D&reserved=0 >>>> >>>> The very first discussion on this was here: >>>> >>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.spinics.net%2Flists%2Fdri-devel%2Fmsg368077.html&data=05%7C01%7Cluben.tuikov%40amd.com%7Cd41da3fd6449492d01f808dab33cdb75%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638019371236833115%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=pSR10abmK8nAMvKSezqWC0SPUBL4qEwtCCizyIKW7Dc%3D&reserved=0 >>>> >>>> Please use this link, and not the that one up there you which quoted above, >>>> and whose commit description is taken verbatim from the this link. >>>> >>>>> >>>>> kset_register() is currently used in some places without calling >>>>> kset_put() in error path, because the callers think it should be >>>>> kset internal thing to do, but the driver core can not know what >>>>> caller doing with that memory at times. The memory could be freed >>>>> both in kset_put() and error path of caller, if it is called in >>>>> kset_register(). >>>> >>>> As I explained in the link above, the reason there's >>>> a memory leak is that one cannot call kset_register() without >>>> the kset->kobj.name being set--kobj_add_internal() returns -EINVAL, >>>> in this case, i.e. kset_register() fails with -EINVAL. >>>> >>>> Thus, the most common usage is something like this: >>>> >>>> kobj_set_name(&kset->kobj, format, ...); >>>> kset->kobj.kset = parent_kset; >>>> kset->kobj.ktype = ktype; >>>> res = kset_register(kset); >>>> >>>> So, what is being leaked, is the memory allocated in kobj_set_name(), >>>> by the common idiom shown above. This needs to be mentioned in >>>> the documentation, at least, in case, in the future this is absolved >>>> in kset_register() redesign, etc. >>> >>> Based on this, can kset_register() just clean up from itself when an >>> error happens? Ideally that would be the case, as the odds of a kset >>> being embedded in a larger structure is probably slim, but we would have >>> to search the tree to make sure. >> >> Looking at kset_register(), we can add kset_put() in the error path, >> when kobject_add_internal(&kset->kobj) fails. >> >> See the attached patch. It needs to be tested with the same error injection >> as Yang has been doing. >> >> Now, struct kset is being embedded in larger structs--see amdgpu_discovery.c >> starting at line 575. If you're on an AMD system, it gets you the tree >> structure you'll see when you run "tree /sys/class/drm/card0/device/ip_discovery/". >> That shouldn't be a problem though. > > Yes, that shouldn't be an issue as the kobject embedded in a kset is > ONLY for that kset itself, the kset structure should not be controling > the lifespan of the object it is embedded in, right? Yes, and it doesn't. It only does a kobject_get(parent) and kobject_put(parent). So that's fine and natural. Yang, do you want to try the patch in my previous email in this thread, since you've got the error injection set up already? Regards, Luben