From patchwork Tue Aug 31 20:16:04 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 504965 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 autolearn=unavailable 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 83053C432BE for ; Tue, 31 Aug 2021 20:16:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A5EA6054E for ; Tue, 31 Aug 2021 20:16:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240899AbhHaURB (ORCPT ); Tue, 31 Aug 2021 16:17:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:46892 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232698AbhHaURA (ORCPT ); Tue, 31 Aug 2021 16:17:00 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D3E3B60238; Tue, 31 Aug 2021 20:16:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1630440965; bh=vrSk7NGDKruQ1GGNei/dolE9sb0nalFXWoxlFB5C8ag=; h=Date:From:To:Subject:From; b=m6Pm6SUM35dJcyPfXTZsMSgGEjbOBkHoIzqT/2ktJ6m2fNIGN5musDyk9rKZXNASH I5QypLdi4eR8RcjAolA0P0mFI9lTTjCP7abEMuzOpx5OvaRlMQUej2+DsvzMDOMgpO 5Uxeb0OaY0TLZ5pW2Mz6za+ZKpSUybRJi2yz1tW0= Date: Tue, 31 Aug 2021 13:16:04 -0700 From: akpm@linux-foundation.org To: guillaume@morinfr.org, mike.kravetz@oracle.com, mm-commits@vger.kernel.org, stable@vger.kernel.org Subject: + hugetlb-fix-hugetlb-cgroup-refcounting-during-vma-split.patch added to -mm tree Message-ID: <20210831201604.JZQfdyjOA%akpm@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: hugetlb: fix hugetlb cgroup refcounting during vma split has been added to the -mm tree. Its filename is hugetlb-fix-hugetlb-cgroup-refcounting-during-vma-split.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/hugetlb-fix-hugetlb-cgroup-refcounting-during-vma-split.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/hugetlb-fix-hugetlb-cgroup-refcounting-during-vma-split.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Mike Kravetz Subject: hugetlb: fix hugetlb cgroup refcounting during vma split Guillaume Morin reported hitting the following WARNING followed by GPF or NULL pointer deference either in cgroups_destroy or in the kill_css path.: percpu ref (css_release) <= 0 (-1) after switching to atomic WARNING: CPU: 23 PID: 130 at lib/percpu-refcount.c:196 percpu_ref_switch_to_atomic_rcu+0x127/0x130 CPU: 23 PID: 130 Comm: ksoftirqd/23 Kdump: loaded Tainted: G O 5.10.60 #1 RIP: 0010:percpu_ref_switch_to_atomic_rcu+0x127/0x130 Call Trace: rcu_core+0x30f/0x530 rcu_core_si+0xe/0x10 __do_softirq+0x103/0x2a2 ? sort_range+0x30/0x30 run_ksoftirqd+0x2b/0x40 smpboot_thread_fn+0x11a/0x170 kthread+0x10a/0x140 ? kthread_create_worker_on_cpu+0x70/0x70 ret_from_fork+0x22/0x30 Upon further examination, it was discovered that the css structure was associated with hugetlb reservations. For private hugetlb mappings the vma points to a reserve map that contains a pointer to the css. At mmap time, reservations are set up and a reference to the css is taken. This reference is dropped in the vma close operation; hugetlb_vm_op_close. However, if a vma is split no additional reference to the css is taken yet hugetlb_vm_op_close will be called twice for the split vma resulting in an underflow. Fix by taking another reference in hugetlb_vm_op_open. Note that the reference is only taken for the owner of the reserve map. In the more common fork case, the pointer to the reserve map is cleared for non-owning vmas. Link: https://lkml.kernel.org/r/20210830215015.155224-1-mike.kravetz@oracle.com Fixes: e9fe92ae0cd2 ("hugetlb_cgroup: add reservation accounting for private mappings") Signed-off-by: Mike Kravetz Reported-by: Guillaume Morin Suggested-by: Guillaume Morin Tested-by: Guillaume Morin Cc: Signed-off-by: Andrew Morton --- include/linux/hugetlb_cgroup.h | 12 ++++++++++++ mm/hugetlb.c | 4 +++- 2 files changed, 15 insertions(+), 1 deletion(-) --- a/include/linux/hugetlb_cgroup.h~hugetlb-fix-hugetlb-cgroup-refcounting-during-vma-split +++ a/include/linux/hugetlb_cgroup.h @@ -121,6 +121,13 @@ static inline void hugetlb_cgroup_put_rs css_put(&h_cg->css); } +static inline void resv_map_dup_hugetlb_cgroup_uncharge_info( + struct resv_map *resv_map) +{ + if (resv_map->css) + css_get(resv_map->css); +} + extern int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages, struct hugetlb_cgroup **ptr); extern int hugetlb_cgroup_charge_cgroup_rsvd(int idx, unsigned long nr_pages, @@ -199,6 +206,11 @@ static inline void hugetlb_cgroup_put_rs { } +static inline void resv_map_dup_hugetlb_cgroup_uncharge_info( + struct resv_map *resv_map) +{ +} + static inline int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages, struct hugetlb_cgroup **ptr) { --- a/mm/hugetlb.c~hugetlb-fix-hugetlb-cgroup-refcounting-during-vma-split +++ a/mm/hugetlb.c @@ -4106,8 +4106,10 @@ static void hugetlb_vm_op_open(struct vm * after this open call completes. It is therefore safe to take a * new reference here without additional locking. */ - if (resv && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) + if (resv && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) { + resv_map_dup_hugetlb_cgroup_uncharge_info(resv); kref_get(&resv->refs); + } } static void hugetlb_vm_op_close(struct vm_area_struct *vma)