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 2D639C001DC for ; Mon, 31 Jul 2023 17:15:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232010AbjGaRPe (ORCPT ); Mon, 31 Jul 2023 13:15:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232128AbjGaRPK (ORCPT ); Mon, 31 Jul 2023 13:15:10 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BFD3326B6 for ; Mon, 31 Jul 2023 10:12:37 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-584341f9cb3so102429087b3.0 for ; Mon, 31 Jul 2023 10:12:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1690823557; x=1691428357; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=c3PYDZ1RN/B3pu1J25lpMbrKPoFg0ktyB6SwecJ4DzU=; b=6FV+nnfj59v0O8qa3GSfbEYQhq8YmdgJWLU8iPRuV+6j61UppVaAn5rOGOl+8YHMdt 5zb59tU4zOXjjNhOid4WniiNCPgSltUe6NgoO/pX6+qFqRqYlePiUlahDQXFWxHbwf7U 5JRbk/t2axk1kdap2kYPs2NLmGWi6QwrywA09T4kw5cif/b+/jnjeTHz4ALKCCdCRMun OfBd07Zdyr5thNsiyTKJzJGNXUd12BPg0pSFSz+ZdMgFAejegH2kK9khBYiJ5O2FuNPa X7b6E6HKN6OD8odj1FJxZrLHyXxOw3Yun7LkiSKkR3ofC+PTL6zZ8gYhvyXgVUdmB4tx AR0g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690823557; x=1691428357; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=c3PYDZ1RN/B3pu1J25lpMbrKPoFg0ktyB6SwecJ4DzU=; b=ZPPhPGWNvPx5BD/jTQl+MNaqizqUmgGm7dzilWTSfFhp+jnMRkbMSmbZGlx1OY6f0c yEb02VA29ILJu7LCLfOzTLTFwWlJ7oOUh9wgH711VeDW8r9XMRSsuQXCDnLQKIrn8//o vWlaaPSJHAo/t3DfWilmOzNwYeECV9aJFw476aTjBB7kEkHzf4iniGAwt/xFTAfYAB4m WlbzUe8IPZ/CsFiJ9HKFKr6b2cLQMN3/sVuyAvjcxe9HtqVZSdVH3f9HKbQpuTJtZunf XfXZD5yWIrbZUaXKadlTVYF4YNc7pVXEt6jvg9abboxTIHkqBnwYv93spjKeR2hSNMII CdWg== X-Gm-Message-State: ABy/qLYfBtn202UjMX/J1zD9nHLq861KS8wnizGVPCngYZBMg6mE8YGP oO6OAzMfI7xyueWHy+DGhuWp3tBiG8k= X-Google-Smtp-Source: APBJJlEKfgHW3Pt+D+HW+X08sGkNnzE7rrwZeKVkKbn6HinHN7XInD85rNYlUT2BXDYNkx/+RNlDUje3uTI= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:201:d4d3:7e41:cb80:21ea]) (user=surenb job=sendgmr) by 2002:a25:305:0:b0:d0c:44d5:4530 with SMTP id 5-20020a250305000000b00d0c44d54530mr115944ybd.3.1690823556992; Mon, 31 Jul 2023 10:12:36 -0700 (PDT) Date: Mon, 31 Jul 2023 10:12:26 -0700 Mime-Version: 1.0 X-Mailer: git-send-email 2.41.0.487.g6d72f3e995-goog Message-ID: <20230731171233.1098105-1-surenb@google.com> Subject: [PATCH 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: stable@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") 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 | 2 +- arch/riscv/mm/pageattr.c | 4 ++-- arch/s390/mm/gmap.c | 10 ++++----- drivers/infiniband/hw/hfi1/file_ops.c | 1 + fs/proc/task_mmu.c | 10 ++++----- fs/userfaultfd.c | 6 +++++ include/linux/mm.h | 13 +++++++---- include/linux/pagewalk.h | 6 ++--- mm/damon/vaddr.c | 4 ++-- mm/hmm.c | 2 +- mm/hugetlb.c | 2 +- mm/khugepaged.c | 5 +++-- mm/ksm.c | 16 +++++++------- mm/madvise.c | 13 +++++------ mm/memcontrol.c | 4 ++-- mm/memory-failure.c | 2 +- mm/memory.c | 2 +- mm/mempolicy.c | 12 ++++------ mm/migrate_device.c | 2 +- mm/mincore.c | 2 +- mm/mlock.c | 5 +++-- mm/mmap.c | 29 ++++++++++++++++--------- mm/mprotect.c | 3 ++- mm/pagewalk.c | 13 ++++++++--- mm/vmscan.c | 3 ++- 26 files changed, 100 insertions(+), 72 deletions(-) -- 2.41.0.487.g6d72f3e995-goog