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 AF0FEC433EF for ; Sat, 4 Jun 2022 19:05:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239954AbiFDTFJ (ORCPT ); Sat, 4 Jun 2022 15:05:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239924AbiFDTFF (ORCPT ); Sat, 4 Jun 2022 15:05:05 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 459F6637B; Sat, 4 Jun 2022 12:05:04 -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 0B34AB802C6; Sat, 4 Jun 2022 19:05:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AA0E5C385B8; Sat, 4 Jun 2022 19:05:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1654369501; bh=VE9DWAYBygq7VbVdUYJ+vmc7mgCTMyNU/Pzz0DVfgZE=; h=Date:To:From:Subject:From; b=hYJ5T7093xpGaKHrbc1XfZr6ydVinudcjNhxHBxUqq2XEfbSgF97fE8mHoVH3Am+n ypF6gFMHFm+gHhQYKGQFLKYATDECP3dWWiWXpXuvBpp9bFUUhKa/wt8nphFuRz5YfJ /BssYd1WZizCqyqd50AljbMGcK4BpwbAImqS5xk8= Date: Sat, 04 Jun 2022 12:05:00 -0700 To: mm-commits@vger.kernel.org, stable@vger.kernel.org, peterx@redhat.com, hughd@google.com, axelrasmussen@google.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-userfaultfd-fix-uffdio_continue-on-fallocated-shmem-pages.patch added to mm-hotfixes-unstable branch Message-Id: <20220604190501.AA0E5C385B8@smtp.kernel.org> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: mm: userfaultfd: fix UFFDIO_CONTINUE on fallocated shmem pages has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-userfaultfd-fix-uffdio_continue-on-fallocated-shmem-pages.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-userfaultfd-fix-uffdio_continue-on-fallocated-shmem-pages.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Axel Rasmussen Subject: mm: userfaultfd: fix UFFDIO_CONTINUE on fallocated shmem pages Date: Fri, 3 Jun 2022 13:57:41 -0700 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/20220603205741.12888-1-axelrasmussen@google.com Fixes: 153132571f02 ("userfaultfd/shmem: support UFFDIO_CONTINUE for shmem") Signed-off-by: Axel Rasmussen Cc: Peter Xu Cc: Hugh Dickins Cc: Signed-off-by: Andrew Morton --- mm/userfaultfd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/userfaultfd.c~mm-userfaultfd-fix-uffdio_continue-on-fallocated-shmem-pages +++ a/mm/userfaultfd.c @@ -246,7 +246,7 @@ 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); if (ret) goto out; if (!page) { _ Patches currently in -mm which might be from axelrasmussen@google.com are mm-userfaultfd-fix-uffdio_continue-on-fallocated-shmem-pages.patch