From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andreas Gruenbacher , Theodore Tso , Jan Kara Subject: [PATCH 4.12 038/106] ext4: fix SEEK_HOLE/SEEK_DATA for blocksize < pagesize Date: Wed, 9 Aug 2017 09:52:22 -0700 Message-Id: <20170809164521.500928439@linuxfoundation.org> In-Reply-To: <20170809164515.714288642@linuxfoundation.org> References: <20170809164515.714288642@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.12-stable 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: Greg Kroah-Hartman --- fs/ext4/file.c | 3 +++ 1 file changed, 3 insertions(+) --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -521,6 +521,8 @@ 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) @@ -535,6 +537,7 @@ 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);