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=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 DB0C8C3F2D1 for ; Wed, 4 Mar 2020 08:56:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B8F472187F for ; Wed, 4 Mar 2020 08:56:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387742AbgCDI4m (ORCPT ); Wed, 4 Mar 2020 03:56:42 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:46279 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727734AbgCDI4m (ORCPT ); Wed, 4 Mar 2020 03:56:42 -0500 Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1j9PpX-00079c-Lj; Wed, 04 Mar 2020 09:56:39 +0100 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id D9DFD101161; Wed, 4 Mar 2020 09:56:37 +0100 (CET) From: Thomas Gleixner To: "Eric W. Biederman" , Qian Cai Cc: oleg@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH timers/core] posix-cpu-timers: Put the task_struct in posix_cpu_timers_create In-Reply-To: <877e00hf08.fsf@x220.int.ebiederm.org> Date: Wed, 04 Mar 2020 09:56:37 +0100 Message-ID: <87wo80lcqi.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ebiederm@xmission.com (Eric W. Biederman) writes: > Qian Cai writes: >> The recent commit removed put_task_struct() in posix_cpu_timer_del() >> results in many memory leaks like this, >> >> 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 >> > > I forgot that get_task_for_clock called by posix_cpu_timer_create > returns a reference to a task_struct. Put that reference > to avoid the leak. I took the liberty to fold this back into the affected commit and add a comment why this put_task_struct() is actually required. Thanks, tglx