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 D4D69C41513 for ; Thu, 3 Aug 2023 17:27:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234724AbjHCR1D (ORCPT ); Thu, 3 Aug 2023 13:27:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42338 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232007AbjHCR05 (ORCPT ); Thu, 3 Aug 2023 13:26:57 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9247030C0 for ; Thu, 3 Aug 2023 10:26:56 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-d1851c52f3dso1293607276.1 for ; Thu, 03 Aug 2023 10:26:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1691083615; x=1691688415; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=cZ2Sq6VO6+Afhr0Ggao6dyfVObiTvoIor2VOxBVDNUQ=; b=cPa0RPACNVX2ZeSvOhETX/ApTMwoNjLDFtBMJdLBKbqOKgAAEKVJMkmX1+OQ7m8oiI nRP9dxXeihwf7k+zwxVZYSLnzRl/3JxkUUNRlD6Gvn/x7J2A7e3AY9bMxKGHDUnYEq5N o8EuuDVdrIS8TSLSQiSFDmCQ6u+OXs1RjNjBxv66OvBImpxNx75I6pIHzHRxbqE1jHx+ MzseOT8F/Kd8sNYb6fBF3zFP8F62hl44NTK/dGbAFtvvwpjb87wyJa64+nJnDfV6zKYS +cd/NndJD0wTB7neqWgh5qF6tawh9ZhwnDWDlfOBAjPlMXZYz+dn+b76zDzzI/KCYrnF 86Tw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1691083615; x=1691688415; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=cZ2Sq6VO6+Afhr0Ggao6dyfVObiTvoIor2VOxBVDNUQ=; b=PQNY3FIaCpYVqyaSCET7kNJFeXarSgrHYASZOSFOkWhlvL5ka73l2TeW63v5nfMdEf pH1cbAZJo2YUdSUSmY1JTrrOT5kS6NnbLkFx4VZq3K/FcKaDEFGYEBPeH4uRvvkecetu zy4MUA6Y5lCIN8HU3BquhPipSuaS/napaMS6ijmLbVVpC//mZH9JytQAgl9ydJzVumn8 bH+qG3+6TLzmx0P1m0Bl2+9mpizSacIs04jp1JtioJ9JCMNQFRS/b1WDRFwdSwfeNjB5 YwMvAqAZEN7JYlJkYjE5F0a+L4D/N1dMaK/yJmqVMonN47lH8d2DZ1wBZwjbEeu1xL2R iP+Q== X-Gm-Message-State: ABy/qLZyM7b5W3gJaG430rZrGtY7onNE7peaIPwh6IFcOoRTjqIH6xz6 rjkOFQ5KuU32LRsZgXOrFceTyoZRnps= X-Google-Smtp-Source: APBJJlHkaDlFGikr7jzCQXoOIxsLN4xYUczw/VwZSwj+TSdWsNmAHDKAVdQ/qIeXeWYgtRctJkUUMzW4e8E= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:201:3dec:ef9e:7bf4:7a6]) (user=surenb job=sendgmr) by 2002:a05:6902:100f:b0:cf9:3564:33cc with SMTP id w15-20020a056902100f00b00cf9356433ccmr181148ybt.13.1691083615709; Thu, 03 Aug 2023 10:26:55 -0700 (PDT) Date: Thu, 3 Aug 2023 10:26:45 -0700 Mime-Version: 1.0 X-Mailer: git-send-email 2.41.0.585.gd2178a4bd4-goog Message-ID: <20230803172652.2849981-1-surenb@google.com> Subject: [PATCH v3 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 v2: - removed vma locking from hfi1_file_mmap(), per Linus - moved vma locking out of dup_anon_vma(), per Liam - 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 and dup_anon_vma 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 ++++ 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 | 32 ++++++++++++++-------- mm/mprotect.c | 2 ++ mm/pagewalk.c | 36 ++++++++++++++++++++++--- mm/vmscan.c | 1 + 25 files changed, 147 insertions(+), 43 deletions(-) -- 2.41.0.585.gd2178a4bd4-goog