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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 265BEC00528 for ; Tue, 1 Aug 2023 22:07:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231366AbjHAWHk (ORCPT ); Tue, 1 Aug 2023 18:07:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33938 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229694AbjHAWHh (ORCPT ); Tue, 1 Aug 2023 18:07:37 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B50FA19B7 for ; Tue, 1 Aug 2023 15:07:36 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id 3f1490d57ef6-c926075a50cso502679276.1 for ; Tue, 01 Aug 2023 15:07:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1690927656; x=1691532456; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=zPqUPKbdP+iIzl/rUw5yUEFwwtlQE8s7qBJDuJeMKGo=; b=q+9OzccPgu9rBNj9tTxxF496DJEUfuPzUq4NJySwfPgbdDOoCMU555Hl/qdgpDWovQ 7P3zZ2+VclqiHfT8jA4l3nOEOoF0zeP3xfx+eBZo8NuKWI2ZlGst5RVijFL/SYmXNX/c EBGSWByJHdwURfZYTxEjjL+Gk5CcvbvFODRPLV4eb+3Hdcu6jAz1S/kBv/TmRram3Lho 5D6Ft49iUVjSDYwIZScsTg7jzmD27EWtWIFAjuv16Hq0nXtyiO4YzEP8YH3AjuH1xlwu TugHF9nnoRBAvRJEC95ny2FaSbtI6beld/hDOO7xdUTap77spYX6TCXHiNvth+9pWjuR OyXw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690927656; x=1691532456; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=zPqUPKbdP+iIzl/rUw5yUEFwwtlQE8s7qBJDuJeMKGo=; b=JolMiHcGT4dP5lUvQJ3VQK4oXhXGFCq158mByVLcil1mEZLY/Zmo837VOpqV+u3xMD A178+1jPdWtfTK1q6CoB3TkcxasBU2HMsnCvk8XGt0ecFWbFrXDB9wknTX4tfzwYlVhW HQBJIZjOEiu4e8D7RV0aXtQl3QRsIqSBJWWguWEhxHr6n05H04TlCmModwyAZesHk9b5 i9DLwukwf2hYztkWpy2bv1jWwpYtLh/FPym0ruUG6jXwSrFSZberp9B5oF9jGw9qbc/I HoX9/HvNnIOTiI7QfeteY2E+7x+St9XX+3jvnuNPTdq2dOQQ6W4DoDsB10NV8Q2y5SCh P3fw== X-Gm-Message-State: ABy/qLat22i58jDLXSY5agr7nyudeJB4VNe1GqbKJJvTeWgasZYl68JY PdztMpsN9+2siBHpIkoSTGIU5CXoRtY= X-Google-Smtp-Source: APBJJlH688tL11JqgwaFAglSA8dGEv9/GHDNslVjpwq0rCCbRaezorHBoZHbvJTwlN1g7j/8quBF3BFvjSU= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:201:211c:a2ff:f17b:c5e9]) (user=surenb job=sendgmr) by 2002:a05:6902:11cb:b0:d16:7ccc:b406 with SMTP id n11-20020a05690211cb00b00d167cccb406mr160911ybu.5.1690927655996; Tue, 01 Aug 2023 15:07:35 -0700 (PDT) Date: Tue, 1 Aug 2023 15:07:26 -0700 Mime-Version: 1.0 X-Mailer: git-send-email 2.41.0.585.gd2178a4bd4-goog Message-ID: <20230801220733.1987762-1-surenb@google.com> Subject: [PATCH v2 0/6] make vma locking more obvious From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org, jannh@google.com, willy@infradead.org, liam.howlett@oracle.com, david@redhat.com, peterx@redhat.com, ldufour@linux.ibm.com, vbabka@suse.cz, michel@lespinasse.org, jglisse@google.com, mhocko@suse.com, hannes@cmpxchg.org, dave@stgolabs.net, hughd@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, Suren Baghdasaryan Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org During recent vma locking patch reviews Linus and Jann Horn noted a number of issues with vma locking and suggested improvements: 1. walk_page_range() does not have ability to write-lock a vma during the walk when it's done under mmap_write_lock. For example s390_reset_cmma(). 2. Vma locking is hidden inside vm_flags modifiers and is hard to follow. Suggestion is to change vm_flags_reset{_once} to assert that vma is write-locked and require an explicit locking. 3. Same issue with vma_prepare() hiding vma locking. 4. In userfaultfd vm_flags are modified after vma->vm_userfaultfd_ctx and page faults can operate on a context while it's changed. 5. do_brk_flags() and __install_special_mapping() not locking a newly created vma before adding it into the mm. While not strictly a problem, this is fragile if vma is modified after insertion, as in the mmap_region() case which was recently fixed. Suggestion is to always lock a new vma before inserting it and making it visible to page faults. 6. vma_assert_write_locked() for CONFIG_PER_VMA_LOCK=n would benefit from being mmap_assert_write_locked() instead of no-op and then any place which operates on a vma and calls mmap_assert_write_locked() can be converted into vma_assert_write_locked(). I CC'ed stable only on the first patch because others are cleanups and the bug in userfaultfd does not affect stable (lock_vma_under_rcu prevents uffds from being handled under vma lock protection). However I would be happy if the whole series is merged into stable 6.4 since it makes vma locking more maintainable. The patches apply cleanly over Linus' ToT and will conflict when applied over mm-unstable due to missing [1]. The conflict can be easily resolved by ignoring conflicting deletions but probably simpler to take [1] into mm-unstable and avoid later conflict. [1] commit 6c21e066f925 ("mm/mempolicy: Take VMA lock before replacing policy") Changes since v1: - replace walk_page_range() parameter with mm_walk_ops.walk_lock, per Linus - introduced page_walk_lock enum to allow different locking modes during a walk, per Linus - added Liam's Reviewed-by Suren Baghdasaryan (6): mm: enable page walking API to lock vmas during the walk mm: for !CONFIG_PER_VMA_LOCK equate write lock assertion for vma and mmap mm: replace mmap with vma write lock assertions when operating on a vma mm: lock vma explicitly before doing vm_flags_reset and vm_flags_reset_once mm: always lock new vma before inserting into vma tree mm: move vma locking out of vma_prepare arch/powerpc/kvm/book3s_hv_uvmem.c | 1 + arch/powerpc/mm/book3s64/subpage_prot.c | 1 + arch/riscv/mm/pageattr.c | 1 + arch/s390/mm/gmap.c | 5 ++++ drivers/infiniband/hw/hfi1/file_ops.c | 1 + fs/proc/task_mmu.c | 5 ++++ fs/userfaultfd.c | 6 +++++ include/linux/mm.h | 13 ++++++--- include/linux/pagewalk.h | 11 ++++++++ mm/damon/vaddr.c | 2 ++ mm/hmm.c | 1 + mm/hugetlb.c | 2 +- mm/khugepaged.c | 5 ++-- mm/ksm.c | 25 ++++++++++------- mm/madvise.c | 8 +++--- mm/memcontrol.c | 2 ++ mm/memory-failure.c | 1 + mm/memory.c | 2 +- mm/mempolicy.c | 22 +++++++++------ mm/migrate_device.c | 1 + mm/mincore.c | 1 + mm/mlock.c | 4 ++- mm/mmap.c | 29 +++++++++++++------- mm/mprotect.c | 2 ++ mm/pagewalk.c | 36 ++++++++++++++++++++++--- mm/vmscan.c | 1 + 26 files changed, 146 insertions(+), 42 deletions(-) -- 2.41.0.585.gd2178a4bd4-goog