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 1F812C433EF for ; Mon, 14 Mar 2022 16:44:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 812786B0071; Mon, 14 Mar 2022 12:44:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7C1868D0002; Mon, 14 Mar 2022 12:44:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 68A508D0001; Mon, 14 Mar 2022 12:44:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0106.hostedemail.com [216.40.44.106]) by kanga.kvack.org (Postfix) with ESMTP id 5B0FD6B0071 for ; Mon, 14 Mar 2022 12:44:32 -0400 (EDT) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 106A2A2AF7 for ; Mon, 14 Mar 2022 16:44:32 +0000 (UTC) X-FDA: 79243565184.20.0383C9D Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by imf02.hostedemail.com (Postfix) with ESMTP id 9084A80011 for ; Mon, 14 Mar 2022 16:44:31 +0000 (UTC) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 3F0BA1F380; Mon, 14 Mar 2022 16:44:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1647276270; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=tkdkWeTfnrxk7PSRlTAb8ziBqg3aEua4BuwGBMwv+gs=; b=mvPZHussDiFs3o5zYNp+zaxs5Pbe7Txeip5Z5UhiQ6fnLlvVv6kllMq1N/WPEzDeK1xU5p WjtQX1NPdIlAt7iajos8ZVvOKkpbjx8bUiI8dALoMk/hUG+cGFadp+F8jqrN5RQlCvGwAc TcnnQrNm099GSsNqPuOnnAgGLHteJG4= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 23CD6A3B88; Mon, 14 Mar 2022 16:44:30 +0000 (UTC) Date: Mon, 14 Mar 2022 17:44:29 +0100 From: Michal Hocko To: Miaohe Lin Cc: akpm@linux-foundation.org, kosaki.motohiro@jp.fujitsu.com, mgorman@suse.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/mempolicy: fix potential mpol_new leak in shared_policy_replace Message-ID: References: <20220311093624.39546-1-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220311093624.39546-1-linmiaohe@huawei.com> X-Rspam-User: X-Rspamd-Queue-Id: 9084A80011 X-Stat-Signature: 796su6589q1jt1oqt3q68rsk8qkd8gnx Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=mvPZHuss; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf02.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com X-Rspamd-Server: rspam03 X-HE-Tag: 1647276271-602462 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: On Fri 11-03-22 17:36:24, Miaohe Lin wrote: > If mpol_new is allocated but not used in restart loop, mpol_new will be > freed via mpol_put before returning to the caller. But refcnt is not > initialized yet, so mpol_put could not do the right things and might > leak the unused mpol_new. The code is really hideous but is there really any bug there? AFAICS the new policy is only allocated in if (n->end > end) branch and that one will set the reference count on the retry. Or am I missing something? > Fixes: 42288fe366c4 ("mm: mempolicy: Convert shared_policy mutex to spinlock") > Signed-off-by: Miaohe Lin > --- > mm/mempolicy.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 34d2b29c96ad..f19f19d3558b 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -2733,6 +2733,7 @@ static int shared_policy_replace(struct shared_policy *sp, unsigned long start, > mpol_new = kmem_cache_alloc(policy_cache, GFP_KERNEL); > if (!mpol_new) > goto err_out; > + refcount_set(&mpol_new->refcnt, 1); > goto restart; > } > > -- > 2.23.0 -- Michal Hocko SUSE Labs