From patchwork Thu Jul 29 20:01:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 489258 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, 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 08491C4320A for ; Thu, 29 Jul 2021 20:01:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E096460F42 for ; Thu, 29 Jul 2021 20:01:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229642AbhG2UBY (ORCPT ); Thu, 29 Jul 2021 16:01:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:43270 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229638AbhG2UBY (ORCPT ); Thu, 29 Jul 2021 16:01:24 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 60C4D60EBC; Thu, 29 Jul 2021 20:01:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1627588880; bh=W5SjuvH5wpnW7xNlfWfTbe2oqoqC7tBV0c9yiwxaXE0=; h=Date:From:To:Subject:From; b=SrnOVOTlysiIqvos+iuPsiar9voUjG3wytgm7K7cgNqVDjhqa9MVjvEVUntNVbzl4 jS9wEC8X7VKoP3pfHFhq/CvO2+ILM7JbtMwl+m7q6RKplnBo2wh2gi/O9RHQVd/Wq8 eCUU2cJ1CZzc+nuDiTHE4hcw26RO4weFi3gVk7Ic= Date: Thu, 29 Jul 2021 13:01:19 -0700 From: akpm@linux-foundation.org To: mm-commits@vger.kernel.org, stable@vger.kernel.org, ptikhomirov@virtuozzo.com, miltonm@bga.com, millerjo@us.ibm.com, manfred@colorfullife.com, ebiederm@xmission.com, dave@stgolabs.net, alexander@mihalicyn.com, alexander.mikhalitsyn@virtuozzo.com Subject: [to-be-updated] shm-skip-shm_destroy-if-task-ipc-namespace-was-changed.patch removed from -mm tree Message-ID: <20210729200119.lnuxr%akpm@linux-foundation.org> User-Agent: s-nail v14.9.10 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: shm: skip shm_destroy if task IPC namespace was changed has been removed from the -mm tree. Its filename was shm-skip-shm_destroy-if-task-ipc-namespace-was-changed.patch This patch was dropped because an updated version will be merged ------------------------------------------------------ From: Alexander Mikhalitsyn Subject: shm: skip shm_destroy if task IPC namespace was changed Patch series "shm: omit forced shm destroy if task IPC namespace was changed". Task IPC namespace shm's has shm_rmid_forced feature which is per IPC namespace and controlled by kernel.shm_rmid_forced sysctl. When feature is turned on, then during task exit (and unshare(CLONE_NEWIPC)) all sysvshm's will be destroyed by exit_shm(struct task_struct *task) function. But there is a problem if task was changed IPC namespace since shmget() call. In such situation exit_shm() function will try to call shm_destroy(, ) which leads to the situation when sysvshm object still attached to old IPC namespace but freed; later during old IPC namespace cleanup we will try to free such sysvshm object for the second time and will get the problem :) First patch solves this problem by postponing shm_destroy to the moment when IPC namespace cleanup will be called. Second patch is useful to prevent (or easy catch) such bugs in the future by adding corresponding WARNings. This patch (of 2): Task may change IPC namespace by doing setns() but sysvshm objects remains at the origin IPC namespace (=IPC namespace where task was when shmget() was called). Let's skip forced shm destroy in such case because we can't determine IPC namespace by shm only. These problematic sysvshm's will be destroyed on ipc namespace cleanup. Link: https://lkml.kernel.org/r/20210706132259.71740-1-alexander.mikhalitsyn@virtuozzo.com Link: https://lkml.kernel.org/r/20210706132259.71740-2-alexander.mikhalitsyn@virtuozzo.com Fixes: ab602f79915 ("shm: make exit_shm work proportional to task activity") Signed-off-by: Alexander Mikhalitsyn Cc: Milton Miller Cc: Jack Miller Cc: Pavel Tikhomirov Cc: Alexander Mikhalitsyn Cc: Manfred Spraul Cc: Davidlohr Bueso Cc: "Eric W. Biederman" Cc: Signed-off-by: Andrew Morton --- ipc/shm.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) --- a/ipc/shm.c~shm-skip-shm_destroy-if-task-ipc-namespace-was-changed +++ a/ipc/shm.c @@ -173,6 +173,14 @@ static inline struct shmid_kernel *shm_o return container_of(ipcp, struct shmid_kernel, shm_perm); } +static inline bool is_shm_in_ns(struct ipc_namespace *ns, struct shmid_kernel *shp) +{ + int idx = ipcid_to_idx(shp->shm_perm.id); + struct shmid_kernel *tshp = shm_obtain_object(ns, idx); + + return !IS_ERR(tshp) && tshp == shp; +} + /* * shm_lock_(check_) routines are called in the paths where the rwsem * is not necessarily held. @@ -415,7 +423,7 @@ void exit_shm(struct task_struct *task) list_for_each_entry_safe(shp, n, &task->sysvshm.shm_clist, shm_clist) { shp->shm_creator = NULL; - if (shm_may_destroy(ns, shp)) { + if (is_shm_in_ns(ns, shp) && shm_may_destroy(ns, shp)) { shm_lock_by_ptr(shp); shm_destroy(ns, shp); }