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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 77E7FC10F26 for ; Mon, 23 Mar 2020 07:22:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5266520732 for ; Mon, 23 Mar 2020 07:22:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727421AbgCWHWE (ORCPT ); Mon, 23 Mar 2020 03:22:04 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:12176 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727164AbgCWHWD (ORCPT ); Mon, 23 Mar 2020 03:22:03 -0400 Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 24D25A297C5B469D6335; Mon, 23 Mar 2020 15:21:52 +0800 (CST) Received: from [127.0.0.1] (10.173.223.234) by DGGEMS413-HUB.china.huawei.com (10.3.19.213) with Microsoft SMTP Server id 14.3.487.0; Mon, 23 Mar 2020 15:21:46 +0800 Subject: Re: [PATCH v2] xfrm: policy: Fix doulbe free in xfrm_policy_timer To: Timo Teras References: <20200318034839.57996-1-yuehaibing@huawei.com> <20200323014155.56376-1-yuehaibing@huawei.com> <20200323085311.35aefe10@vostro.wlan> CC: , , , , , From: Yuehaibing Message-ID: <832e03ea-2511-eb7f-49d1-3cda6c9e6d18@huawei.com> Date: Mon, 23 Mar 2020 15:21:45 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20200323085311.35aefe10@vostro.wlan> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.173.223.234] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/3/23 14:53, Timo Teras wrote: > Hi > > On Mon, 23 Mar 2020 09:41:55 +0800 > YueHaibing wrote: > >> After xfrm_add_policy add a policy, its ref is 2, then >> >> xfrm_policy_timer >> read_lock >> xp->walk.dead is 0 >> .... >> mod_timer() >> xfrm_policy_kill >> policy->walk.dead = 1 >> .... >> del_timer(&policy->timer) >> xfrm_pol_put //ref is 1 >> xfrm_pol_put //ref is 0 >> xfrm_policy_destroy >> call_rcu >> xfrm_pol_hold //ref is 1 >> read_unlock >> xfrm_pol_put //ref is 0 >> xfrm_policy_destroy >> call_rcu >> >> xfrm_policy_destroy is called twice, which may leads to >> double free. > > I believe the timer changes were added later in commit e7d8f6cb2f which > added holding a reference when timer is running. I think it fails to > properly account for concurrently running timer in xfrm_policy_kill(). commit e7d8f6cb2f hold a reference when &pq->hold_timer is armed, in my case, it's policy->timer, and hold_timer is not armed. > > The time when commit ea2dea9dacc2 was done this was not the case. > > I think it would be preferable if the concurrency issue could be solved > without additional locking. > >> Call Trace: >> RIP: 0010:refcount_warn_saturate+0x161/0x210 >> ... >> xfrm_policy_timer+0x522/0x600 >> call_timer_fn+0x1b3/0x5e0 >> ? __xfrm_decode_session+0x2990/0x2990 >> ? msleep+0xb0/0xb0 >> ? _raw_spin_unlock_irq+0x24/0x40 >> ? __xfrm_decode_session+0x2990/0x2990 >> ? __xfrm_decode_session+0x2990/0x2990 >> run_timer_softirq+0x5c5/0x10e0 >> >> Fix this by use write_lock_bh in xfrm_policy_kill. >> >> Fixes: ea2dea9dacc2 ("xfrm: remove policy lock when accessing >> policy->walk.dead") Signed-off-by: YueHaibing > > Should be instead: > Fixes: e7d8f6cb2f ("xfrm: Add refcount handling to queued policies") > >> --- >> v2: Fix typo 'write_lock_bh'--> 'write_unlock_bh' while unlocking >> --- >> net/xfrm/xfrm_policy.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c >> index dbda08ec566e..ae0689174bbf 100644 >> --- a/net/xfrm/xfrm_policy.c >> +++ b/net/xfrm/xfrm_policy.c >> @@ -434,6 +434,7 @@ EXPORT_SYMBOL(xfrm_policy_destroy); >> >> static void xfrm_policy_kill(struct xfrm_policy *policy) >> { >> + write_lock_bh(&policy->lock); >> policy->walk.dead = 1; >> >> atomic_inc(&policy->genid); >> @@ -445,6 +446,7 @@ static void xfrm_policy_kill(struct xfrm_policy >> *policy) if (del_timer(&policy->timer)) >> xfrm_pol_put(policy); >> >> + write_unlock_bh(&policy->lock); >> xfrm_pol_put(policy); >> } >> > > > . >