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 X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 D26CAC388D1 for ; Tue, 13 Oct 2020 02:42:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9EF1720678 for ; Tue, 13 Oct 2020 02:42:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=arista.com header.i=@arista.com header.b="CYzWXkjH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728276AbgJMBea (ORCPT ); Mon, 12 Oct 2020 21:34:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57394 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728255AbgJMBe2 (ORCPT ); Mon, 12 Oct 2020 21:34:28 -0400 Received: from mail-wr1-x442.google.com (mail-wr1-x442.google.com [IPv6:2a00:1450:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3C4D1C0613D8 for ; Mon, 12 Oct 2020 18:34:28 -0700 (PDT) Received: by mail-wr1-x442.google.com with SMTP id b8so8620754wrn.0 for ; Mon, 12 Oct 2020 18:34:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arista.com; s=googlenew; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=o+hT7zzmskqvyrywNbGv1SqYy6yeRy0QTDltdgYSbdc=; b=CYzWXkjHBNX+YU71eO5qpuuPH6qwUIdqJ/91p3uYMEMCdZAKCSTrNpq5TVbhmE0CD3 I/VxDj5wkbfpz7t0kQmbILNl/5EseAGLKDK8dCemcemqrzP3b56toQhhE3rNbnkWmkmm AICs1qLVVt2lax+VdQCmztePp5r0dg4+rFYAPJGdEALV5rSwyMg9LJiqUmL79gPixms9 ntjlR6MHQ1kYOjnTSbioqJvPiK4/DfA2peP3dpqJYRhN6pOfIolRGMfCAz3AdiWY+SBD Hjd8PJdjC3spCD+xAvw0TX9aA0hdWnJyRznCUfgv2rcesWONvNxkVjwNeIhJxKvga2lq sbdA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=o+hT7zzmskqvyrywNbGv1SqYy6yeRy0QTDltdgYSbdc=; b=bF6YGNEFp9GjzSjdbaNud9tYaCfQ4ACoI2em9N2w35LsXQzQ937euRQuLXPf+R97YS SCJeV2AI2t0Q8uGb/Z27tkTWy43LGm25X41hFXa/pV85CsBkk5GE9RG0hHlTjyLOQgvW Pvux0c2ubof8FIUdK33uMxubFAOx14bO88wYLT1D387Ea1bDxPXYgLcx6JnGyUsI5WGP r3iBtVIYgkeSfs1QKwRTF7olBf+pmLp1Ydkn/wJ44D8O0oc26bdrnYptYk/jqDgYSvNe nv2qeOXi1tRVtcheJx7ZEaG5p0k0dVzpp5+sImxqzQVMbOS6IqT/ridASWi30WLwWJwp Aj9g== X-Gm-Message-State: AOAM533Z3JLNMJqvwcCWYht4FTzIVwLmZ2JEW1Naz3+9IH28fmjaXWO7 0eZu6mm8mEeMuD8EwGEorkkWXiYzjkwE4yco X-Google-Smtp-Source: ABdhPJx/eA0xaURdD39kuIvNIumfP2FJFkk5wEpy22MoNkD2iAsN3onMEMvZoLmBi3z0b1VkhtsO1w== X-Received: by 2002:a5d:4c8d:: with SMTP id z13mr16731759wrs.412.1602552866741; Mon, 12 Oct 2020 18:34:26 -0700 (PDT) Received: from localhost.localdomain ([2a02:8084:e84:2480:228:f8ff:fe6f:83a8]) by smtp.gmail.com with ESMTPSA id d23sm24825325wmb.6.2020.10.12.18.34.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Oct 2020 18:34:26 -0700 (PDT) From: Dmitry Safonov To: linux-kernel@vger.kernel.org Cc: Dmitry Safonov <0x7f454c46@gmail.com>, Dmitry Safonov , Alexander Viro , Andrew Morton , Andy Lutomirski , Brian Geffon , Catalin Marinas , Dan Williams , Dave Jiang , Hugh Dickins , Ingo Molnar , "Kirill A. Shutemov" , Mike Kravetz , Minchan Kim , Russell King , Thomas Bogendoerfer , Thomas Gleixner , Vishal Verma , Vlastimil Babka , Will Deacon , linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 5/6] mremap: Check if it's possible to split original vma Date: Tue, 13 Oct 2020 02:34:15 +0100 Message-Id: <20201013013416.390574-6-dima@arista.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201013013416.390574-1-dima@arista.com> References: <20201013013416.390574-1-dima@arista.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If original VMA can't be split at the desired address, do_munmap() will fail and leave both new-copied VMA and old VMA. De-facto it's MREMAP_DONTUNMAP behaviour, which is unexpected. Currently, it may fail such way for hugetlbfs and dax device mappings. Minimize such unpleasant situations to OOM by checking .may_split() before attempting to create a VMA copy. Signed-off-by: Dmitry Safonov --- mm/mremap.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/mm/mremap.c b/mm/mremap.c index 898e9818ba6d..3c4047c23673 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -343,7 +343,7 @@ static unsigned long move_vma(struct vm_area_struct *vma, unsigned long excess = 0; unsigned long hiwater_vm; int split = 0; - int err; + int err = 0; bool need_rmap_locks; /* @@ -353,6 +353,15 @@ static unsigned long move_vma(struct vm_area_struct *vma, if (mm->map_count >= sysctl_max_map_count - 3) return -ENOMEM; + if (vma->vm_ops && vma->vm_ops->may_split) { + if (vma->vm_start != old_addr) + err = vma->vm_ops->may_split(vma, old_addr); + if (!err && vma->vm_end != old_addr + old_len) + err = vma->vm_ops->may_split(vma, old_addr + old_len); + if (err) + return err; + } + /* * Advise KSM to break any KSM pages in the area to be moved: * it would be confusing if they were to turn up at the new -- 2.28.0