From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0107CD0BB4A for ; Thu, 24 Oct 2024 01:26:43 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8C3D76B0085; Wed, 23 Oct 2024 21:26:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8748C6B0088; Wed, 23 Oct 2024 21:26:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 73C026B0089; Wed, 23 Oct 2024 21:26:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 5456A6B0085 for ; Wed, 23 Oct 2024 21:26:43 -0400 (EDT) Received: from smtpin24.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 9323B120F34 for ; Thu, 24 Oct 2024 01:26:26 +0000 (UTC) X-FDA: 82706755740.24.A5849CD Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) by imf25.hostedemail.com (Postfix) with ESMTP id E6F12A0018 for ; Thu, 24 Oct 2024 01:26:21 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=none; spf=pass (imf25.hostedemail.com: domain of chenridong@huaweicloud.com designates 45.249.212.51 as permitted sender) smtp.mailfrom=chenridong@huaweicloud.com; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1729733048; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+RbvscWhB7+MtE5tbSyHtNt/wgAH6GhaAqEEwqZMvnU=; b=Aopsd6mZD1dz6xA0gSEn2q2uGOHJaRTOlmu3y3oe+1Y+d80idwccdriXA/tUWe+7mDSDCa Xw2FEWGN3CY8if/Bf2Pk5/UngEiXgp+l5LQGnpKMM5sGMphOvD2iJgbYtC6Cfm2wTAAv1K jG/ZQydmtM0QwnJweuoNneoEPqlJKeo= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1729733048; a=rsa-sha256; cv=none; b=ru9JcWd9F+Ns7fBiAcfBzKnWFwUen98fvP/+29nRmPHqLQutcDYDxBw2y21GrhEi+4jYyh HrWGufGDea60lptCv92mPXWo4YZUFN5PumkkDdnqBPP6wkUisfRdviWr+eRFmt9fYNXi5j hZ9xSyC+XWUz167GkdldMihSbSb9XLU= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=none; spf=pass (imf25.hostedemail.com: domain of chenridong@huaweicloud.com designates 45.249.212.51 as permitted sender) smtp.mailfrom=chenridong@huaweicloud.com; dmarc=none Received: from mail.maildlp.com (unknown [172.19.93.142]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4XYpCX0h64z4f3jt9 for ; Thu, 24 Oct 2024 09:26:16 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.75]) by mail.maildlp.com (Postfix) with ESMTP id 6F5211A07B6 for ; Thu, 24 Oct 2024 09:26:28 +0800 (CST) Received: from [10.67.109.79] (unknown [10.67.109.79]) by APP2 (Coremail) with SMTP id Syh0CgAHPGFBohlnBra7Ew--.27167S2; Thu, 24 Oct 2024 09:26:26 +0800 (CST) Message-ID: Date: Thu, 24 Oct 2024 09:26:24 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: shrinker: avoid memleak in alloc_shrinker_info To: Roman Gushchin , Vlastimil Babka , akpm@linux-foundation.org, david@fromorbit.com Cc: Muchun Song , Anshuman Khandual , "Kirill A. Shutemov" , akpm@linux-foundation.org, david@fromorbit.com, zhengqi.arch@bytedance.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, wangweiyang2@huawei.com References: <1BD74B20-879A-4159-B957-1223553217C1@linux.dev> <0b883f9e-451f-41c2-805f-7f5bc7eebee2@suse.cz> Content-Language: en-US From: Chen Ridong In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-CM-TRANSID:Syh0CgAHPGFBohlnBra7Ew--.27167S2 X-Coremail-Antispam: 1UD129KBjvJXoW3GFykuF43GF4ktrW5WFW3Wrg_yoWxGFWxpF WfGFy2kF4kJr1UJr12q3W5Jr18tw4jy3WUXrn3Jry8Arn09F15Jr17Jr48CryDGryxAr12 qrZ8XrW2vryUA3DanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUv0b4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JM4IIrI8v6xkF7I0E8cxan2IY04v7MxkF7I0En4kS 14v26r1q6r43MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I 8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUtVW8 ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x 0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_ Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7IU1 7KsUUUUUU== X-CM-SenderInfo: hfkh02xlgr0w46kxt4xhlfz01xgou0bp/ X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: E6F12A0018 X-Stat-Signature: r73jrqozxtm47dop71kncs8g6yygtrcm X-HE-Tag: 1729733181-468699 X-HE-Meta: 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 +SSaIvm1 vyOwDlJsMI7B1t3SPruzvMYdSM/JdLuNrK9Wvm+QXwFBttESdxP83AbGgqLTHrNXzfVYSIB2zKgY/yphz8uTCEnuVT50CWeiejJeMM7O+QJNXl1wBTAy/YHF8Jb5NX7SdBlKRQuv16S/IHrurBiP37fVPSWdcZN6KJ6J6itm7rsYCoTHQ7mBmICaLcULQ0dZB5biU77Ivsh218jc9PJ0QcdLQ80ufmuL4BZGkhFoV4VqA2nxIpwREdWGqtKsZXruZoHBKwddVMzP3SKR8HfkWPvso83Bf2gIRvnRT0xokJooNJ4JUZPaApokglVMt431PdUue X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2024/10/17 1:31, Roman Gushchin wrote: > On Wed, Oct 16, 2024 at 07:02:23PM +0200, Vlastimil Babka wrote: >> On 10/16/24 16:08, Muchun Song wrote: >>> >>> >>>> On Oct 16, 2024, at 19:43, Vlastimil Babka wrote: >>>> On 10/16/24 04:21, Muchun Song wrote: >>>>> >>>>> >>>>>> On Oct 16, 2024, at 09:25, chenridong wrote: >>>>>> On 2024/10/15 14:55, Anshuman Khandual wrote: >>>>>>> On 10/14/24 16:59, Kirill A. Shutemov wrote: >>>>>>>> On Mon, Oct 14, 2024 at 03:23:36AM +0000, Chen Ridong wrote: >>>>>>>>> From: Chen Ridong >>>>>>>>> A memleak was found as bellow: >>>>>>>>> unreferenced object 0xffff8881010d2a80 (size 32): >>>>>>>>> comm "mkdir", pid 1559, jiffies 4294932666 >>>>>>>>> hex dump (first 32 bytes): >>>>>>>>> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >>>>>>>>> 40 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 @............... >>>>>>>>> backtrace (crc 2e7ef6fa): >>>>>>>>> [] __kmalloc_node_noprof+0x394/0x470 >>>>>>>>> [] alloc_shrinker_info+0x7b/0x1a0 >>>>>>>>> [] mem_cgroup_css_online+0x11a/0x3b0 >>>>>>>>> [] online_css+0x29/0xa0 >>>>>>>>> [] cgroup_apply_control_enable+0x20d/0x360 >>>>>>>>> [] cgroup_mkdir+0x168/0x5f0 >>>>>>>>> [] kernfs_iop_mkdir+0x5e/0x90 >>>>>>>>> [] vfs_mkdir+0x144/0x220 >>>>>>>>> [] do_mkdirat+0x87/0x130 >>>>>>>>> [] __x64_sys_mkdir+0x49/0x70 >>>>>>>>> [] do_syscall_64+0x68/0x140 >>>>>>>>> [] entry_SYSCALL_64_after_hwframe+0x76/0x7e >>>>>>>>> In the alloc_shrinker_info function, when shrinker_unit_alloc return >>>>>>>>> err, the info won't be freed. Just fix it. >>>>>>>>> Fixes: 307bececcd12 ("mm: shrinker: add a secondary array for shrinker_info::{map, nr_deferred}") >>>>>>>>> Signed-off-by: Chen Ridong >>>>>>>>> --- >>>>>>>>> mm/shrinker.c | 1 + >>>>>>>>> 1 file changed, 1 insertion(+) >>>>>>>>> diff --git a/mm/shrinker.c b/mm/shrinker.c >>>>>>>>> index dc5d2a6fcfc4..92270413190d 100644 >>>>>>>>> --- a/mm/shrinker.c >>>>>>>>> +++ b/mm/shrinker.c >>>>>>>>> @@ -97,6 +97,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg) >>>>>>>>> err: >>>>>>>>> mutex_unlock(&shrinker_mutex); >>>>>>>>> + kvfree(info); >>>>>>>>> free_shrinker_info(memcg); >>>>>>>>> return -ENOMEM; >>>>>>>>> } >>>>>>>> NAK. If in the future there going to one more error case after >>>>>>>> rcu_assign_pointer() we will end up with double free. >>>>>>>> This should be safer: >>>>>>>> diff --git a/mm/shrinker.c b/mm/shrinker.c >>>>>>>> index dc5d2a6fcfc4..763fd556bc7d 100644 >>>>>>>> --- a/mm/shrinker.c >>>>>>>> +++ b/mm/shrinker.c >>>>>>>> @@ -87,8 +87,10 @@ int alloc_shrinker_info(struct mem_cgroup *memcg) >>>>>>>> if (!info) >>>>>>>> goto err; >>>>>>>> info->map_nr_max = shrinker_nr_max; >>>>>>>> - if (shrinker_unit_alloc(info, NULL, nid)) >>>>>>>> + if (shrinker_unit_alloc(info, NULL, nid)) { >>>>>>>> + kvfree(info); >>>>>>>> goto err; >>>>>>>> + } >>>>>>>> rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info); >>>>>>>> } >>>>>>>> mutex_unlock(&shrinker_mutex); >>>>>>> Agreed, this is what I mentioned earlier as well. >>>>>>> ------------------------------------------------------------------ >>>>>>> I guess kvfree() should be called just after shrinker_unit_alloc() >>>>>>> fails but before calling into "goto err" >>>>>>> ------------------------------------------------------------------ >>>>>> After discussion, it seems that v1 is acceptable. >>>>>> Hi, Muchun, do you have any other opinions? >>>>> >>>>> I insist on my opinion, not mixing two different approaches >>>>> to do release resources. >>>> >>>> So instead we mix the cleanup of the whole function with the cleanup of what >>>> is effectively a per-iteration temporary variable? >>>> >>>> The fact there was already a confusion in this thread about whether it's >>>> safe and relies on kvfree(NULL) to be a no-op, should be a hint. >>> >>> Yes. I think someone is confused about my opinion. >>> I don’t care about whether we should apply this hit. >>> If we think the hint is tricky, we could add another >>> label to fix it like I suggested previously. Because >>> we already use goto-based approaches to >>> cleanup the resources, why not keeping >>> consistent? >> >> I think we're rather pragmatic than striving to be consistent for the sake >> of consistency. goto is not the nicest thing in the world, but we (unlike >> other projects) use it where it makes sense to avoid if/else nesting >> explosion. Here for the info it's not the most pragmatic option. >> >>> It will be easier for us to add a new >>> "if" statement and handle the failure case in the future. >> >> Let's not overengineer things for hypothetical future. >> >>> For example, if we use his v1 proposal, we should do >>> the cleanups again for info. But for goto-based >>> version, we just add another label to do the >>> cleanups and go to the new label for failure case. goto-based fix is what I insisted on. I copied my previous suggested fix here to clarify my opinion. >> >> Again, info is a loop-iteration-local variable, v1 fix making it truly local >> is the way to go. If there are further cleanups added in the loop itself in >> the future, they could hopefully keep being local to the loop as well. >> Cleanup of info outside the loop iteration is breaking its real scope. > > +1 to that. > > I don't think it's such a big deal and both versions are ok, but I strongly > prefer the original version (without introduction of a new label). > > Please, feel free to use > Acked-by: Roman Gushchin > with the original version. > > Thanks! I agree with Roman. Hello, Andrew and Dave, Do you have any opinions? The original version: https://lore.kernel.org/linux-kernel/4184c61f-80f7-4adc-8929-c29f959cb8df@huawei.com/ Best regards, Ridong