From patchwork Mon Aug 26 10:18:23 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Max Reitz X-Patchwork-Id: 269886 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id D9AB02C00C4 for ; Mon, 26 Aug 2013 23:36:55 +1000 (EST) Received: from localhost ([::1]:51482 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VDwyT-0005K5-8M for incoming@patchwork.ozlabs.org; Mon, 26 Aug 2013 09:36:53 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58635) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VDtt8-0001hS-EO for qemu-devel@nongnu.org; Mon, 26 Aug 2013 06:19:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VDtsz-00041o-O8 for qemu-devel@nongnu.org; Mon, 26 Aug 2013 06:19:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:14182) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VDtsz-00041b-Fl for qemu-devel@nongnu.org; Mon, 26 Aug 2013 06:19:01 -0400 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r7QAJ0C0016423 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 26 Aug 2013 06:19:01 -0400 Received: from localhost (dhcp-200-247.str.redhat.com [10.33.200.247]) by int-mx02.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id r7QAIxMV029860 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO); Mon, 26 Aug 2013 06:19:00 -0400 From: Max Reitz To: qemu-devel@nongnu.org Date: Mon, 26 Aug 2013 12:18:23 +0200 Message-Id: <1377512306-27382-3-git-send-email-mreitz@redhat.com> In-Reply-To: <1377512306-27382-1-git-send-email-mreitz@redhat.com> References: <1377512306-27382-1-git-send-email-mreitz@redhat.com> X-Scanned-By: MIMEDefang 2.67 on 10.5.11.12 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 X-Mailman-Approved-At: Mon, 26 Aug 2013 09:34:41 -0400 Cc: kwolf@redhat.com, Max Reitz Subject: [Qemu-devel] [PATCH 2/5] qcow2: Metadata overlap checks 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 Two new functions are added; the first one checks a given range in the image file for overlaps with metadata (main header, L1 tables, L2 tables, refcount table and blocks). The second one should be used immediately before writing to the image file as it calls the first function and, upon collision, marks the image as corrupt and makes the BDS unusable, thereby preventing further access. Both functions take a bitmask argument specifying the structures which should be checked for overlaps, making it possible to also check metadata writes against colliding with other structures. Signed-off-by: Max Reitz --- block/qcow2-refcount.c | 142 +++++++++++++++++++++++++++++++++++++++++++++++++ block/qcow2.h | 28 ++++++++++ 2 files changed, 170 insertions(+) diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 1244693..c8141c8 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -25,6 +25,7 @@ #include "qemu-common.h" #include "block/block_int.h" #include "block/qcow2.h" +#include "qemu/range.h" static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size); static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs, @@ -1372,3 +1373,144 @@ fail: return ret; } +/* + * Checks if the given offset into the image file is actually free to use by + * looking for overlaps with important metadata sections (L1/L2 tables etc.), + * i.e. a sanity check without relying on the refcount tables. + * + * The chk parameter specifies exactly what checks to perform. + * + * Returns: + * - 0 if writing to this offset will not affect the mentioned metadata + * - a positive QCow2MetadataOverlap value indicating one overlapping section + * - a negative value (-errno) indicating an error while performing a check, + * e.g. when bdrv_read failed on QCOW2_OL_INACTIVE_L2 + */ +int qcow2_check_metadata_overlap(BlockDriverState *bs, QCow2MetadataOverlap chk, + int64_t offset, int64_t size) +{ + BDRVQcowState *s = bs->opaque; + int i, j; + + if (!size) { + return 0; + } + + if (chk & QCOW2_OL_MAIN_HEADER) { + if (offset < s->cluster_size) { + return QCOW2_OL_MAIN_HEADER; + } + } + + if ((chk & QCOW2_OL_ACTIVE_L1) && s->l1_size) { + if (ranges_overlap(offset, size, s->l1_table_offset, + s->l1_size * sizeof(uint64_t))) { + return QCOW2_OL_ACTIVE_L1; + } + } + + if ((chk & QCOW2_OL_REFCOUNT_TABLE) && s->refcount_table_size) { + if (ranges_overlap(offset, size, s->refcount_table_offset, + s->refcount_table_size * sizeof(uint64_t))) { + return QCOW2_OL_REFCOUNT_TABLE; + } + } + + if ((chk & QCOW2_OL_SNAPSHOT_TABLE) && s->snapshots_size) { + if (ranges_overlap(offset, size, s->snapshots_offset, + s->snapshots_size)) { + return QCOW2_OL_SNAPSHOT_TABLE; + } + } + + if ((chk & QCOW2_OL_INACTIVE_L1) && s->snapshots) { + for (i = 0; i < s->nb_snapshots; i++) { + if (s->snapshots[i].l1_size && + ranges_overlap(offset, size, s->snapshots[i].l1_table_offset, + s->snapshots[i].l1_size * sizeof(uint64_t))) { + return QCOW2_OL_INACTIVE_L1; + } + } + } + + if ((chk & QCOW2_OL_ACTIVE_L2) && s->l1_table) { + for (i = 0; i < s->l1_size; i++) { + if ((s->l1_table[i] & L1E_OFFSET_MASK) && + ranges_overlap(offset, size, s->l1_table[i] & L1E_OFFSET_MASK, + s->cluster_size)) { + return QCOW2_OL_ACTIVE_L2; + } + } + } + + if ((chk & QCOW2_OL_REFCOUNT_BLOCK) && s->refcount_table) { + for (i = 0; i < s->refcount_table_size; i++) { + if ((s->refcount_table[i] & REFT_OFFSET_MASK) && + ranges_overlap(offset, size, s->refcount_table[i] & + REFT_OFFSET_MASK, s->cluster_size)) { + return QCOW2_OL_REFCOUNT_BLOCK; + } + } + } + + if ((chk & QCOW2_OL_INACTIVE_L2) && s->snapshots) { + for (i = 0; i < s->nb_snapshots; i++) { + uint64_t l1_ofs = s->snapshots[i].l1_table_offset; + uint32_t l1_sz = s->snapshots[i].l1_size; + uint64_t *l1 = g_malloc(l1_sz * sizeof(uint64_t)); + int ret; + + ret = bdrv_read(bs->file, l1_ofs / BDRV_SECTOR_SIZE, (uint8_t *)l1, + l1_sz * sizeof(uint64_t) / BDRV_SECTOR_SIZE); + + if (ret < 0) { + g_free(l1); + return ret; + } + + for (j = 0; j < l1_sz; j++) { + if ((l1[j] & L1E_OFFSET_MASK) && + ranges_overlap(offset, size, l1[j] & L1E_OFFSET_MASK, + s->cluster_size)) { + g_free(l1); + return QCOW2_OL_INACTIVE_L2; + } + } + + g_free(l1); + } + } + + return 0; +} + +/* + * First performs a check for metadata overlaps (through + * qcow2_check_metadata_overlap); if that fails with a negative value (error + * while performing a check), it will print a message but otherwise ignore that + * error. If an impending overlap is detected, the BDS will be made unusable and + * the qcow2 file marked corrupt. + * + * Returns 0 if there were no overlaps (or an error occured while checking for + * overlaps) or a positive QCow2MetadataOverlap value on overlap (then, the BDS + * will be unusable and the qcow2 file marked corrupt). + */ +int qcow2_pre_write_overlap_check(BlockDriverState *bs, QCow2MetadataOverlap chk, + int64_t offset, int64_t size) +{ + int ret = qcow2_check_metadata_overlap(bs, chk, offset, size); + + if (ret < 0) { + fprintf(stderr, "qcow2: Error while checking for metadata overlaps: " + "%s\n", strerror(-ret)); + return ret; + } else if (ret > 0) { + fprintf(stderr, "qcow2: Preventing invalid write on metadata; " + "image marked as corrupt.\n"); + qcow2_mark_corrupt(bs); + bs->drv = NULL; /* make BDS unusable */ + return ret; + } + + return 0; +} diff --git a/block/qcow2.h b/block/qcow2.h index 4297487..8a55da0 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -289,6 +289,29 @@ enum { QCOW2_CLUSTER_ZERO }; +typedef enum QCow2MetadataOverlap { + QCOW2_OL_NONE = 0, + QCOW2_OL_MAIN_HEADER = (1 << 0), + QCOW2_OL_ACTIVE_L1 = (1 << 1), + QCOW2_OL_ACTIVE_L2 = (1 << 2), + QCOW2_OL_REFCOUNT_TABLE = (1 << 3), + QCOW2_OL_REFCOUNT_BLOCK = (1 << 4), + QCOW2_OL_SNAPSHOT_TABLE = (1 << 5), + QCOW2_OL_INACTIVE_L1 = (1 << 6), + /* NOTE: Checking overlaps with inactive L2 tables will result in bdrv + * reads. */ + QCOW2_OL_INACTIVE_L2 = (1 << 7), +} QCow2MetadataOverlap; + +/* Perform all overlap checks which don't require disk access */ +#define QCOW2_OL_CACHED \ + (QCOW2_OL_MAIN_HEADER | QCOW2_OL_ACTIVE_L1 | QCOW2_OL_ACTIVE_L2 | \ + QCOW2_OL_REFCOUNT_TABLE | QCOW2_OL_REFCOUNT_BLOCK | \ + QCOW2_OL_SNAPSHOT_TABLE | QCOW2_OL_INACTIVE_L1) + +/* The default checks to perform */ +#define QCOW2_OL_DEFAULT QCOW2_OL_CACHED + #define L1E_OFFSET_MASK 0x00ffffffffffff00ULL #define L2E_OFFSET_MASK 0x00ffffffffffff00ULL #define L2E_COMPRESSED_OFFSET_SIZE_MASK 0x3fffffffffffffffULL @@ -390,6 +413,11 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res, void qcow2_process_discards(BlockDriverState *bs, int ret); +int qcow2_check_metadata_overlap(BlockDriverState *bs, QCow2MetadataOverlap chk, + int64_t offset, int64_t size); +int qcow2_pre_write_overlap_check(BlockDriverState *bs, QCow2MetadataOverlap chk, + int64_t offset, int64_t size); + /* qcow2-cluster.c functions */ int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size, bool exact_size);