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=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 60556C83007 for ; Wed, 29 Apr 2020 21:50:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1EB6420757 for ; Wed, 29 Apr 2020 21:50:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="rpSOhgpZ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1EB6420757 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 B6E278E000A; Wed, 29 Apr 2020 17:50:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AFAB08E0001; Wed, 29 Apr 2020 17:50:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A0D9C8E000A; Wed, 29 Apr 2020 17:50:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0174.hostedemail.com [216.40.44.174]) by kanga.kvack.org (Postfix) with ESMTP id 8669A8E0001 for ; Wed, 29 Apr 2020 17:50:28 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 438E2181AC9CB for ; Wed, 29 Apr 2020 21:50:28 +0000 (UTC) X-FDA: 76762236936.03.wall79_40e22323d62d X-HE-Tag: wall79_40e22323d62d X-Filterd-Recvd-Size: 4767 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) by imf41.hostedemail.com (Postfix) with ESMTP for ; Wed, 29 Apr 2020 21:50:27 +0000 (UTC) Received: by mail-yb1-f201.google.com with SMTP id n205so5238095ybf.14 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=OltetA21h9NTF8swDMJ6/ae7n4kJDJpR3JH0mISal5VLdh+qr0mxqHQ0wqvlDHUzDp 43zcz5vlbfvTSLiIXHavjTVqRnMKiycbxmLnXOXeY9W7lGYmj1GEgn/AtKddcP0H51E7 GZdhNLa7t5XQYIABfJgr3Wps6TLbcIhaRWeiaaWmuBLmhttCzi9b19oNjKofbLj3pnr6 voneXiKbb86PgYadpMtQDzpe84BhjRAItbNCyJhsYiLgzyAMU7snRV/2Floa/KC6Rcyc 9uET25us9DE1DJuwquhsVV8rETVK3l/tU0V+33oOSPCDI1LnN/rB+P/hXIOwMBfWZYKt kcDw== X-Gm-Message-State: AGi0PubYdJq6rGke5005vWSAhJyFaAMiL8/YiUnRy9FtgpMsEx5T1ebV h70Q5MxqLAI4pke7gIOwvdHPaGj4Bg== 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" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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