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=-20.4 required=3.0 tests=BAYES_00,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=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 1D1FBC433EA for ; Tue, 18 Aug 2020 06:13:07 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D854A2075B for ; Tue, 18 Aug 2020 06:13:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ZwNZMdOm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D854A2075B Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8192E8D0007; Tue, 18 Aug 2020 02:13:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7A0718D0001; Tue, 18 Aug 2020 02:13:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6DCA78D0007; Tue, 18 Aug 2020 02:13:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0164.hostedemail.com [216.40.44.164]) by kanga.kvack.org (Postfix) with ESMTP id 580448D0001 for ; Tue, 18 Aug 2020 02:13:06 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 1F9E6181AEF1F for ; Tue, 18 Aug 2020 06:13:06 +0000 (UTC) X-FDA: 77162671572.17.wood06_350af932701d Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin17.hostedemail.com (Postfix) with ESMTP id E7654180D0181 for ; Tue, 18 Aug 2020 06:13:05 +0000 (UTC) X-HE-Tag: wood06_350af932701d X-Filterd-Recvd-Size: 4445 Received: from mail-qv1-f73.google.com (mail-qv1-f73.google.com [209.85.219.73]) by imf26.hostedemail.com (Postfix) with ESMTP for ; Tue, 18 Aug 2020 06:13:05 +0000 (UTC) Received: by mail-qv1-f73.google.com with SMTP id d19so12516499qvm.23 for ; Mon, 17 Aug 2020 23:13:05 -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=uEsosFURBjONd+/+zLGkVplNTPfQUMPsbnxJn8l+5vc=; b=ZwNZMdOmDrLPGKWoU7+xUPQWuT5oFIHuub4ejn1ekJsju5Wwy4BLyJBNVFY7s7BOld z3j7VbHfP0i4lVA1JENTx0vcSL03Ivy7dRS9ixIgK6o9EnEGMJMVSN27CQhbCwLUUGja g2kOE4ob+pHuuCV3lxWoW781kDluCgRGWDnAPhZxeaR/O94K6cNgRXgdK/AQ0tq08LM/ HTnNGkc2Hr1LW06qlLL1igs/cd0cIwr/k5am8Yq+ZUlq2W/bZqQPuN/yvos43bmZzKui vGmfTNebqL+H4H3PJeXssHpUinSJ181aWS1QvdMT+BzOZLkJTgY+MgaAplPmApsiySYe alww== 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=uEsosFURBjONd+/+zLGkVplNTPfQUMPsbnxJn8l+5vc=; b=aLgOtmMiODzyy19jcdF3QWjVqhoJpdgCLO8OHOOW6fnRb/NC44hKVIHVGlxAHX59Gg CFmdy1DlScz1U+gjV0/AxSs0HHROXo3wP0Ei/YGKn6VA8s+r18gLAG1hpz+LT2Qx34a7 fY+3cOcBzzykbWUEwgzKSbTYtxtRsB7kWZkkS1loxgn8kw2WZg9/M+dQAdiVh1tl1oCM n2IlGyzqYoeXqMYFjl1lJgCQo/DHQphj/ChOJsVwp63jyR+kw/ZqN2TbAP7CSrsfCu3t iAmb5V9Vozsxx652B//ZtC4nnbftPkJnqOX3qsV99Y3Zke6XdYOc6MOC7Q9RCzQS9Q3d w8jg== X-Gm-Message-State: AOAM533GULE3VIFKORu10AcVqPl9KUxkQ6c/PTJ/WTlowOk1/sOYxVmE a+q8Ag0fGcDoKj8yPhF9YEQihtaM+Q== X-Google-Smtp-Source: ABdhPJxP3VNaCKztfKGOZRUkeGpGigQsg+G3JDfTvOzuksmwqiQeamW72iYG3Jd8rw3YImyyUmlMeGtIjQ== X-Received: by 2002:ad4:40cb:: with SMTP id x11mr18084057qvp.176.1597731184753; Mon, 17 Aug 2020 23:13:04 -0700 (PDT) Date: Tue, 18 Aug 2020 08:12:39 +0200 In-Reply-To: <20200818061239.29091-1-jannh@google.com> Message-Id: <20200818061239.29091-6-jannh@google.com> Mime-Version: 1.0 References: <20200818061239.29091-1-jannh@google.com> X-Mailer: git-send-email 2.28.0.220.ged08abb693-goog Subject: [PATCH v3 5/5] mm/gup: Take mmap_lock 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 Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: E7654180D0181 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Properly take the mmap_lock before calling into the GUP code from get_dump_page(); and play nice, allowing the GUP code to drop the mmap_lock 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 | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 92519e5a44b3..bd0f7311c5c6 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1552,19 +1552,23 @@ static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start, * 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_lock, but after all other threads have been killed. + * Called without mmap_lock (takes and releases the mmap_lock by itself). */ #ifdef CONFIG_ELF_CORE 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_locked(current->mm, addr, 1, &page, &vma, NULL, - FOLL_FORCE | FOLL_DUMP | FOLL_GET) < 1) + if (mmap_read_lock_killable(mm)) return NULL; - flush_cache_page(vma, addr, page_to_pfn(page)); - return page; + ret = __get_user_pages_locked(mm, addr, 1, &page, NULL, &locked, + FOLL_FORCE | FOLL_DUMP | FOLL_GET); + if (locked) + mmap_read_unlock(mm); + return (ret == 1) ? page : NULL; } #endif /* CONFIG_ELF_CORE */ -- 2.28.0.220.ged08abb693-goog