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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 8C038C3F2D1 for ; Wed, 4 Mar 2020 05:18:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 67A392146E for ; Wed, 4 Mar 2020 05:18:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726141AbgCDFSE (ORCPT ); Wed, 4 Mar 2020 00:18:04 -0500 Received: from out02.mta.xmission.com ([166.70.13.232]:38602 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725283AbgCDFSD (ORCPT ); Wed, 4 Mar 2020 00:18:03 -0500 Received: from in01.mta.xmission.com ([166.70.13.51]) by out02.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1j9MPp-0007RD-8g; Tue, 03 Mar 2020 22:17:53 -0700 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1j9MPo-0000FJ-Fj; Tue, 03 Mar 2020 22:17:53 -0700 From: ebiederm@xmission.com (Eric W. Biederman) To: Qian Cai Cc: tglx@linutronix.de, oleg@redhat.com, linux-kernel@vger.kernel.org References: <20200304004336.960-1-cai@lca.pw> Date: Tue, 03 Mar 2020 23:15:43 -0600 In-Reply-To: <20200304004336.960-1-cai@lca.pw> (Qian Cai's message of "Tue, 3 Mar 2020 19:43:36 -0500") Message-ID: <87eeu8hf9c.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1j9MPo-0000FJ-Fj;;;mid=<87eeu8hf9c.fsf@x220.int.ebiederm.org>;;;hst=in01.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/FMuuJ1tVH9jD5uBGuCXk2Slxsx30rT5M= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH -next] posix-cpu-timers: fix memory leaks for task_struct X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Qian Cai writes: > The recent commit removed put_task_struct() in posix_cpu_timer_del() > results in many memory leaks like this, Good spotting but no. The leak is in posix_cpu_timer_create. There is a strong likely hood but no guarantee that the task in posix_cpu_timer_del is the same as the task in posix_cpu_timer_create. Plus the point of it all is to use pid references instead of task references. Thank you very much for catching my braino. Eric > unreferenced object 0xc0000016d9b44480 (size 8192): > comm "timer_create01", pid 57749, jiffies 4295163733 (age 6159.670s) > hex dump (first 32 bytes): > 02 00 00 00 00 00 00 00 10 00 00 00 00 00 00 00 ................ > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > backtrace: > [<0000000056aca129>] copy_process+0x26c/0x18e0 > alloc_task_struct_node at kernel/fork.c:169 > (inlined by) dup_task_struct at kernel/fork.c:877 > (inlined by) copy_process at kernel/fork.c:1929 > [<00000000bdbbf9f8>] _do_fork+0xac/0xb20 > [<00000000dcb1c445>] __do_sys_clone+0x98/0xe0 > __do_sys_clone at kernel/fork.c:2591 > [<000000006c059205>] ppc_clone+0x8/0xc > ppc_clone at arch/powerpc/kernel/entry_64.S:479 > > Fixes: 672ebe8eb017a5 ("posix-cpu-timers: Store a reference to a pid not a task") > Signed-off-by: Qian Cai > --- > kernel/time/posix-cpu-timers.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c > index afd1e959a282..e0b580deb61a 100644 > --- a/kernel/time/posix-cpu-timers.c > +++ b/kernel/time/posix-cpu-timers.c > @@ -446,8 +446,10 @@ static int posix_cpu_timer_del(struct k_itimer *timer) > > out: > rcu_read_unlock(); > - if (!ret) > + if (!ret) { > put_pid(ctmr->pid); > + put_task_struct(p); > + } > > return ret; > }