From patchwork Wed Oct 10 05:56:35 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Cody X-Patchwork-Id: 190548 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 8F1662C0084 for ; Wed, 10 Oct 2012 16:56:59 +1100 (EST) Received: from localhost ([::1]:52865 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TLpHt-0007H5-Lg for incoming@patchwork.ozlabs.org; Wed, 10 Oct 2012 01:56:57 -0400 Received: from eggs.gnu.org ([208.118.235.92]:55190) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TLpHk-0007Gw-Pi for qemu-devel@nongnu.org; Wed, 10 Oct 2012 01:56:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TLpHe-00049s-Ul for qemu-devel@nongnu.org; Wed, 10 Oct 2012 01:56:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53461) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TLpHe-00049N-Kh for qemu-devel@nongnu.org; Wed, 10 Oct 2012 01:56:42 -0400 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q9A5ufwT023851 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Wed, 10 Oct 2012 01:56:42 -0400 Received: from localhost ([10.3.112.7]) by int-mx12.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id q9A5udhr017696 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO); Wed, 10 Oct 2012 01:56:41 -0400 From: Jeff Cody To: qemu-devel@nongnu.org Date: Wed, 10 Oct 2012 01:56:35 -0400 Message-Id: <37ca1a150224c144f9329fc8408f78c388f50a02.1349848348.git.jcody@redhat.com> In-Reply-To: References: In-Reply-To: References: X-Scanned-By: MIMEDefang 2.68 on 10.5.11.25 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 209.132.183.28 Cc: kwolf@redhat.com, pbonzini@redhat.com Subject: [Qemu-devel] [PATCH 1/2] block: make bdrv_find_backing_image compare canonical filenames X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Currently, bdrv_find_backing_image compares bs->backing_file with what is passed in as a backing_file name. Mismatches may occur, however, when bs->backing_file and backing_file are both not absolute or relative. Use path_combine() to make sure any relative backing filenames are relative to the current image filename being searched, and then use realpath() to make all comparisons based on absolute filenames. This also changes bdrv_find_backing_image to no longer be recursive, but iterative. Signed-off-by: Jeff Cody Reviewed-by: Paolo Bonzini Reviewed-by: Eric Blake --- block.c | 38 ++++++++++++++++++++++++++++++++------ 1 file changed, 32 insertions(+), 6 deletions(-) diff --git a/block.c b/block.c index e95f613..641b8fa 100644 --- a/block.c +++ b/block.c @@ -3123,18 +3123,44 @@ int bdrv_snapshot_load_tmp(BlockDriverState *bs, return -ENOTSUP; } +/* backing_file can either be relative, or absolute. If it is + * relative, it must be relative to the chain. So, passing in + * bs->filename from a BDS as backing_file should not be done, + * as that may be relative to the CWD rather than the chain. */ BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs, const char *backing_file) { - if (!bs->drv) { + char filename_full[PATH_MAX]; + char backing_file_full[PATH_MAX]; + char filename_tmp[PATH_MAX]; + BlockDriverState *curr_bs = NULL; + + if (!bs || !bs->drv) { return NULL; } - if (bs->backing_hd) { - if (strcmp(bs->backing_file, backing_file) == 0) { - return bs->backing_hd; - } else { - return bdrv_find_backing_image(bs->backing_hd, backing_file); + for (curr_bs = bs; curr_bs->backing_hd; curr_bs = curr_bs->backing_hd) { + /* If not an absolute filename path, make it relative to the current + * image's filename path */ + path_combine(filename_tmp, sizeof(filename_tmp), + curr_bs->filename, backing_file); + + /* We are going to compare absolute pathnames */ + if (!realpath(filename_tmp, filename_full)) { + continue; + } + + /* We need to make sure the backing filename we are comparing against + * is relative to the current image filename (or absolute) */ + path_combine(filename_tmp, sizeof(filename_tmp), + curr_bs->filename, curr_bs->backing_file); + + if (!realpath(filename_tmp, backing_file_full)) { + continue; + } + + if (strcmp(backing_file_full, filename_full) == 0) { + return curr_bs->backing_hd; } }