From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933517AbdKGAOC (ORCPT ); Mon, 6 Nov 2017 19:14:02 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:53586 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933427AbdKGAMg (ORCPT ); Mon, 6 Nov 2017 19:12:36 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Jan Kara" , "Theodore Ts'o" , "Andreas Gruenbacher" Date: Mon, 06 Nov 2017 23:03:02 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 095/294] ext4: fix SEEK_HOLE/SEEK_DATA for blocksize < pagesize In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.50-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Jan Kara commit fcf5ea10992fbac3c7473a1db33d56a139333cd1 upstream. ext4_find_unwritten_pgoff() does not properly handle a situation when starting index is in the middle of a page and blocksize < pagesize. The following command shows the bug on filesystem with 1k blocksize: xfs_io -f -c "falloc 0 4k" \ -c "pwrite 1k 1k" \ -c "pwrite 3k 1k" \ -c "seek -a -r 0" foo In this example, neither lseek(fd, 1024, SEEK_HOLE) nor lseek(fd, 2048, SEEK_DATA) will return the correct result. Fix the problem by neglecting buffers in a page before starting offset. Reported-by: Andreas Gruenbacher Signed-off-by: Theodore Ts'o Signed-off-by: Jan Kara Signed-off-by: Ben Hutchings --- fs/ext4/file.c | 3 +++ 1 file changed, 3 insertions(+) --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -344,6 +344,8 @@ static int ext4_find_unwritten_pgoff(str lastoff = page_offset(page); bh = head = page_buffers(page); do { + if (lastoff + bh->b_size <= startoff) + goto next; if (buffer_uptodate(bh) || buffer_unwritten(bh)) { if (whence == SEEK_DATA) @@ -358,6 +360,7 @@ static int ext4_find_unwritten_pgoff(str unlock_page(page); goto out; } +next: lastoff += bh->b_size; bh = bh->b_this_page; } while (bh != head);