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=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL 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 CD2F8C83007 for ; Wed, 29 Apr 2020 21:50:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9C1E020757 for ; Wed, 29 Apr 2020 21:50:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="rpSOhgpZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727890AbgD2Vub (ORCPT ); Wed, 29 Apr 2020 17:50:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46204 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1727875AbgD2Vu2 (ORCPT ); Wed, 29 Apr 2020 17:50:28 -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 DE481C03C1AE for ; Wed, 29 Apr 2020 14:50:27 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id w15so5155106ybp.16 for ; Wed, 29 Apr 2020 14:50:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=j9WUvKonPgTjIUwjN6gAw2Ow91kmiZMiVo0dKn965xM=; b=rpSOhgpZAHdOAwMyVgY0CFeQV4JBSuitbsj273BpBIYbY5RLsc4oU8PEL0H8l2TB5Q jG553aIKfQF2YF6o13fsBMT5zGN9segQ20ek4BoudBSd1oldgaKUIzQE1gUENm6VWCJL rwV8ZCHjEEotGPzpCJokeDTsN3sON5Be1JY9+ilHhlCYSwmVmYep7UjgmJeL0j+AtidP A/WuYCLR/baWvIOOSlanC6XH+h7tjaSu5ed9lIJtvsjuLczSBPgDCXkkJ+gL9HeXObZ4 LPEB4qS5TfOwPWx/cfdcs+Q13OO74wWcsFq39oxOHl9vj9OcZRqB9BpSiip4xH6q2UDi xagA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=j9WUvKonPgTjIUwjN6gAw2Ow91kmiZMiVo0dKn965xM=; b=SWnSSrSI6pGBjjp4OSYhdzJ+H5cmfGYEeZ747Ej5qVV2efAuuVzLlXckeBjy+J5hxY +VM+6piQ7ivcAx8P0/ZPTjpn2q36lknaiTvXXHw4hRUuDqLCcVzrtLX+tAd7ftOioeJb wtl++1SNmaMb5C5BpNXBvsNLnSPPnRh7eJvSAkk60rKS2t0jg7eTrdsS9DUOb4KBY/XI pXPSKgqd8pezNxCifBuEf3LLASemjoaOyo3YFa3UWGibAuFqkyG/QznxCKdq9yVAmHg9 /s0Rg3CvEKfvU3ILypMlkQ8V12rwaUbGYse4K0ggd0pbiYvQQk2wRCd3n8uvOLbCsyNI s3/g== X-Gm-Message-State: AGi0PuYMiNC+5ngEUuRJKDK4avjwZrLsJQKsvqhKwaV5BUM4BCAOW4QM lGxTMVHEN93E40f87h2rZ6veM3nVig== X-Google-Smtp-Source: APiQypIHJ7rV1yTDZpZYpBo1v+hnjoUzGur3b82l9wJsRlWX+KQ5lDvvOT4btIQYmN3rHDSbWDUnK04YhA== X-Received: by 2002:a25:23d4:: with SMTP id j203mr618266ybj.97.1588197027087; Wed, 29 Apr 2020 14:50:27 -0700 (PDT) Date: Wed, 29 Apr 2020 23:49:54 +0200 In-Reply-To: <20200429214954.44866-1-jannh@google.com> Message-Id: <20200429214954.44866-6-jannh@google.com> Mime-Version: 1.0 References: <20200429214954.44866-1-jannh@google.com> X-Mailer: git-send-email 2.26.2.526.g744177e7f7-goog Subject: [PATCH v2 5/5] mm/gup: Take mmap_sem in get_dump_page() From: Jann Horn To: Andrew Morton Cc: Linus Torvalds , Christoph Hellwig , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Alexander Viro , "Eric W . Biederman" , Oleg Nesterov , Russell King , linux-arm-kernel@lists.infradead.org, Mark Salter , Aurelien Jacquiot , linux-c6x-dev@linux-c6x.org, Yoshinori Sato , Rich Felker , linux-sh@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Properly take the mmap_sem before calling into the GUP code from get_dump_page(); and play nice, allowing the GUP code to drop the mmap_sem if it has to sleep. As Linus pointed out, we don't actually need the VMA because __get_user_pages() will flush the dcache for us if necessary. Signed-off-by: Jann Horn --- mm/gup.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 9a7e83772f1fe..03f659ddd830a 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1548,19 +1548,23 @@ static long __get_user_pages_locked(struct task_struct *tsk, * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found - * allowing a hole to be left in the corefile to save diskspace. * - * Called without mmap_sem, but after all other threads have been killed. + * Called without mmap_sem (takes and releases the mmap_sem by itself). */ struct page *get_dump_page(unsigned long addr) { - struct vm_area_struct *vma; + struct mm_struct *mm = current->mm; struct page *page; + int locked = 1; + int ret; - if (__get_user_pages(current, current->mm, addr, 1, - FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma, - NULL) < 1) + if (down_read_killable(&mm->mmap_sem)) return NULL; - flush_cache_page(vma, addr, page_to_pfn(page)); - return page; + ret = __get_user_pages_locked(current, mm, addr, 1, &page, NULL, + &locked, + FOLL_FORCE | FOLL_DUMP | FOLL_GET); + if (locked) + up_read(&mm->mmap_sem); + return (ret == 1) ? page : NULL; } #if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA) -- 2.26.2.526.g744177e7f7-goog