From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id B9E21185936 for ; Tue, 15 Oct 2024 06:55:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728975346; cv=none; b=jYW3Qb/oR2ErXfn5F5p8x4O+KleQ3UA02YWOzjtunCTU8ABeyAVQiIbC7OFd8e2XwU+N/4UF/gBNPG/YlKwGT19uN50CBf0moBOn6OJarn89THN9QCSqJ0yaEFr6fQZcO7Yj6XRFgDrmLv/nDffUYOpTEvBi+2gAicul4CYpjd8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728975346; c=relaxed/simple; bh=XFtOcK6cW5q2TN85YbMm7gAqu9WmsY9zhmgQ56U0ysI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hNlmyQbZLG8eyQzhUGRU+NfLmbCsg2KY6IjpCMKUHHqqSdHShNdXrqRAF602jZIbsR5O6WLaLeYutBxAa5y0tOnCqeCSqIciJNE9URqAtzk9BUGaCDWfjrJE2NJJuxFlT64Cb0itB2gafxAs3ePgZg7UYzZN3ideMkOfdwSgPT0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 761811063; Mon, 14 Oct 2024 23:56:13 -0700 (PDT) Received: from [10.162.16.109] (a077893.blr.arm.com [10.162.16.109]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F0CB23F51B; Mon, 14 Oct 2024 23:55:40 -0700 (PDT) Message-ID: Date: Tue, 15 Oct 2024 12:25:38 +0530 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: "Kirill A. Shutemov" , Chen Ridong Cc: akpm@linux-foundation.org, david@fromorbit.com, zhengqi.arch@bytedance.com, roman.gushchin@linux.dev, muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, chenridong@huawei.com, wangweiyang2@huawei.com References: <20241014032336.482088-1-chenridong@huaweicloud.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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" ------------------------------------------------------------------