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 025C6C43334 for ; Tue, 19 Jul 2022 12:50:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241776AbiGSMuU (ORCPT ); Tue, 19 Jul 2022 08:50:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39946 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241667AbiGSMsm (ORCPT ); Tue, 19 Jul 2022 08:48:42 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8A45D8D5DE; Tue, 19 Jul 2022 05:19:12 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id C87B1B81B10; Tue, 19 Jul 2022 12:18:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2436FC341C6; Tue, 19 Jul 2022 12:18:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1658233128; bh=rgXUttIrCJXhvzmAYfs7u6gm3QoGgvQv12sDrFaR+NQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=saoscKWLpcMEYxPjuCCHKFRUasGZNXccDEkqiKKPAR+GTsPRNtXkdYHkNCU1V55kQ zpqZUwsBthor76/OgeA3HC2/EpENZH+nr4Y8ZOT5C8nkrqJtrkfi/B+Gcm6+sJJ5dz ZQ1nnVv/Ml8OVkEs2gr+9zJcNY0KYPJ1lj17Yo1U= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Axel Rasmussen , Peter Xu , Hugh Dickins , Andrew Morton Subject: [PATCH 5.18 016/231] mm: userfaultfd: fix UFFDIO_CONTINUE on fallocated shmem pages Date: Tue, 19 Jul 2022 13:51:41 +0200 Message-Id: <20220719114715.404069935@linuxfoundation.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220719114714.247441733@linuxfoundation.org> References: <20220719114714.247441733@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Axel Rasmussen commit 73f37dbcfe1763ee2294c7717a1f571e27d17fd8 upstream. When fallocate() is used on a shmem file, the pages we allocate can end up with !PageUptodate. Since UFFDIO_CONTINUE tries to find the existing page the user wants to map with SGP_READ, we would fail to find such a page, since shmem_getpage_gfp returns with a "NULL" pagep for SGP_READ if it discovers !PageUptodate. As a result, UFFDIO_CONTINUE returns -EFAULT, as it would do if the page wasn't found in the page cache at all. This isn't the intended behavior. UFFDIO_CONTINUE is just trying to find if a page exists, and doesn't care whether it still needs to be cleared or not. So, instead of SGP_READ, pass in SGP_NOALLOC. This is the same, except for one critical difference: in the !PageUptodate case, SGP_NOALLOC will clear the page and then return it. With this change, UFFDIO_CONTINUE works properly (succeeds) on a shmem file which has been fallocated, but otherwise not modified. Link: https://lkml.kernel.org/r/20220610173812.1768919-1-axelrasmussen@google.com Fixes: 153132571f02 ("userfaultfd/shmem: support UFFDIO_CONTINUE for shmem") Signed-off-by: Axel Rasmussen Acked-by: Peter Xu Cc: Hugh Dickins Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/userfaultfd.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -231,7 +231,10 @@ static int mcontinue_atomic_pte(struct m struct page *page; int ret; - ret = shmem_getpage(inode, pgoff, &page, SGP_READ); + ret = shmem_getpage(inode, pgoff, &page, SGP_NOALLOC); + /* Our caller expects us to return -EFAULT if we failed to find page. */ + if (ret == -ENOENT) + ret = -EFAULT; if (ret) goto out; if (!page) {