From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7BD2113633F for ; Wed, 16 Oct 2024 01:25:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.187 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729041940; cv=none; b=kfcjF94LD51IDyJp4LDmOddTQujsPcTFD2G2izYnujGJXaFIPwCqzfDZa0OS0n5KdprYfAmOZOOr5nqInJyyZ24TUES97kyOJ3FA72Ru+zjzMRLD5EQVyfs1PMMe/S9liSznJHQLuIMc4WbA2pWxdfkHDcvz2Az8B1bGhQ8tQO4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729041940; c=relaxed/simple; bh=XgaUC5ekKLsytnPS231NZ0ExKIN/6afzoYhrLXC6Z5Y=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=WuTdQXRD/t7GCmLqHGT95iYNQPSDAmmVkk0diFPoQh1lFRhN3CmmdO8c3/ZzhDGHpqlpQqtmFXw2wapakE9ZgzTQRXfJUeD/Nh5sj4pU76NTQvqGp68hRD2fvysYg2tUP7VkXSE1Sz+QOnEMa6Ez4YrcN3l8Aedw/QYTT/YvkVc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.187 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.174]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4XStXJ2bJQz10Nf8; Wed, 16 Oct 2024 09:23:44 +0800 (CST) Received: from kwepemd100013.china.huawei.com (unknown [7.221.188.163]) by mail.maildlp.com (Postfix) with ESMTPS id 97969140157; Wed, 16 Oct 2024 09:25:36 +0800 (CST) Received: from [10.67.109.79] (10.67.109.79) by kwepemd100013.china.huawei.com (7.221.188.163) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1258.34; Wed, 16 Oct 2024 09:25:35 +0800 Message-ID: <4a18e997-3a94-4248-8923-c3764d12b0d6@huawei.com> Date: Wed, 16 Oct 2024 09:25:34 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: shrinker: avoid memleak in alloc_shrinker_info To: Anshuman Khandual , "Kirill A. Shutemov" , Muchun Song CC: , , , , , , , References: <20241014032336.482088-1-chenridong@huaweicloud.com> Content-Language: en-US From: chenridong In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemd100013.china.huawei.com (7.221.188.163) 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? Best regards, Ridong