From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta0.migadu.com (out-182.mta0.migadu.com [91.218.175.182]) (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 078D513D2BC for ; Mon, 14 Oct 2024 08:44:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728895496; cv=none; b=CGoKYLST91lm3seNmvwRYaWFwopD8RyLI3F62BgFVLJdsfxWGS/RALAnfkvurwwf7Bb0+sY6ZPl+fdRPIMW/gupbqVRg38Y0onYnLJcV3aQy3HJ55nRdaWcrnUNaj2LxMFkWTndsasyCCxvapUX2UGXYR+lJ+5pA8VpsiabRbxg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728895496; c=relaxed/simple; bh=6a1aFNvCP8oSQhfNPDpQjZyDszaUOOVaxqTozcN7CHo=; h=Content-Type:Mime-Version:Subject:From:In-Reply-To:Date:Cc: Message-Id:References:To; b=KG3nGoh91PVALMy8rCD26afIT6xn/T8a6/gDGyaKf+zJkTol8qD4M2MAKQ13eYqp2iMGdu6DxhZ+KephWedJFTet0Wf4Avr0USAKsLDB5AaADvDQfGaiijkCDXzZrvzQKHt9y6mFLvUYEfT+3ua3/mGheBCwr0Y83/F/RrXGWmg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=eUXjikBZ; arc=none smtp.client-ip=91.218.175.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="eUXjikBZ" Content-Type: text/plain; charset=us-ascii DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1728895491; h=from:from: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=8HymtqTchiQpzME33HIhPmrfIpt1fflEw+LjEVZN4OU=; b=eUXjikBZo/wbyW+I2zALGFaqZCtk+WaTncA+wFsPHiACMY1PAFz8oeEkbOiudDy+S3gSZd m4LICcK5Ao/JkSsyS3x/srpyIwHPxY1kPbbh7cuml4zAv2K45bv0FC0mbNtvK+SUTHyTwC gQC1cwKcVsCO8hCuchpY2rCXiVwSrUo= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3818.100.11.1.3\)) Subject: Re: [PATCH v2] mm: shrinker: avoid memleak in alloc_shrinker_info X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Muchun Song In-Reply-To: Date: Mon, 14 Oct 2024 16:43:59 +0800 Cc: akpm@linux-foundation.org, david@fromorbit.com, zhengqi.arch@bytedance.com, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, chenridong@huawei.com, wangweiyang2@huawei.com Content-Transfer-Encoding: quoted-printable Message-Id: <178A7AC8-0BDA-42CA-86B2-E1C13F3E1E8B@linux.dev> References: <20241014032336.482088-1-chenridong@huaweicloud.com> To: Anshuman Khandual , Chen Ridong X-Migadu-Flow: FLOW_OUT > On Oct 14, 2024, at 16:13, Anshuman Khandual = wrote: >=20 >=20 >=20 > On 10/14/24 08:53, Chen Ridong wrote: >> From: Chen Ridong >>=20 >> A memleak was found as bellow: >>=20 >> 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 >>=20 >> In the alloc_shrinker_info function, when shrinker_unit_alloc return >> err, the info won't be freed. Just fix it. >>=20 >> 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(+) >>=20 >> 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) >>=20 >> err: >> mutex_unlock(&shrinker_mutex); >> + kvfree(info); >> free_shrinker_info(memcg); >> return -ENOMEM; >> } >=20 > There are two scenarios when "goto err:" gets called >=20 > - When shrinker_info allocations fails, no kvfree() is required > - but after this change kvfree() would be called even > when the allocation had failed originally, which does > not sound right Yes. In this case, @info is NULL and kvfree could handle NULL. It seems strange but the final behaviour correct. >=20 > - shrinker_unit_alloc() fails, kvfree() is actually required >=20 > I guess kvfree() should be called just after shrinker_unit_alloc() > fails but before calling into "goto err". We could do it like this, which avoids ambiguity (if someone ignores that kvfree could handle NULL). Something like: --- a/mm/shrinker.c +++ b/mm/shrinker.c @@ -88,13 +88,14 @@ int alloc_shrinker_info(struct mem_cgroup *memcg) goto err; info->map_nr_max =3D shrinker_nr_max; if (shrinker_unit_alloc(info, NULL, nid)) - goto err; + goto free; rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, = info); } mutex_unlock(&shrinker_mutex); return ret; - +free: + kvfree(info); err: mutex_unlock(&shrinker_mutex); free_shrinker_info(memcg); Thanks. >=20 > But curious, should not both kvzalloc_node()/kvfree() be avoided > while inside mutex lock to avoid possible lockdep issues ?