diff options
Diffstat (limited to 'block/qcow2-refcount.c')
| -rw-r--r-- | block/qcow2-refcount.c | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index a61224a414..8ee2f13604 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -25,6 +25,8 @@ #include "qemu-common.h" #include "block/block_int.h" #include "block/qcow2.h" +#include "qemu/range.h" +#include "qapi/qmp/types.h" static int64_t alloc_clusters_noref(BlockDriverState *bs, int64_t size); static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs, @@ -1390,3 +1392,173 @@ fail: return ret; } +#define overlaps_with(ofs, sz) \ + ranges_overlap(offset, size, ofs, sz) + +/* + * 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 (being a bitmask + * of QCow2MetadataOverlap values). + * + * 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, int 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; + } + } + + /* align range to test to cluster boundaries */ + size = align_offset(offset_into_cluster(s, offset) + size, s->cluster_size); + offset = start_of_cluster(s, offset); + + if ((chk & QCOW2_OL_ACTIVE_L1) && s->l1_size) { + if (overlaps_with(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 (overlaps_with(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 (overlaps_with(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 && + overlaps_with(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) && + overlaps_with(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) && + overlaps_with(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) && + overlaps_with(l1[j] & L1E_OFFSET_MASK, s->cluster_size)) { + g_free(l1); + return QCOW2_OL_INACTIVE_L2; + } + } + + g_free(l1); + } + } + + return 0; +} + +static const char *metadata_ol_names[] = { + [QCOW2_OL_MAIN_HEADER_BITNR] = "qcow2_header", + [QCOW2_OL_ACTIVE_L1_BITNR] = "active L1 table", + [QCOW2_OL_ACTIVE_L2_BITNR] = "active L2 table", + [QCOW2_OL_REFCOUNT_TABLE_BITNR] = "refcount table", + [QCOW2_OL_REFCOUNT_BLOCK_BITNR] = "refcount block", + [QCOW2_OL_SNAPSHOT_TABLE_BITNR] = "snapshot table", + [QCOW2_OL_INACTIVE_L1_BITNR] = "inactive L1 table", + [QCOW2_OL_INACTIVE_L2_BITNR] = "inactive L2 table", +}; + +/* + * First performs a check for metadata overlaps (through + * qcow2_check_metadata_overlap); if that fails with a negative value (error + * while performing a check), that value is returned. If an impending overlap + * is detected, the BDS will be made unusable, the qcow2 file marked corrupt + * and -EIO returned. + * + * Returns 0 if there were neither overlaps nor errors while checking for + * overlaps; or a negative value (-errno) on error. + */ +int qcow2_pre_write_overlap_check(BlockDriverState *bs, int chk, int64_t offset, + int64_t size) +{ + int ret = qcow2_check_metadata_overlap(bs, chk, offset, size); + + if (ret < 0) { + return ret; + } else if (ret > 0) { + int metadata_ol_bitnr = ffs(ret) - 1; + char *message; + QObject *data; + + assert(metadata_ol_bitnr < QCOW2_OL_MAX_BITNR); + + fprintf(stderr, "qcow2: Preventing invalid write on metadata (overlaps " + "with %s); image marked as corrupt.\n", + metadata_ol_names[metadata_ol_bitnr]); + message = g_strdup_printf("Prevented %s overwrite", + metadata_ol_names[metadata_ol_bitnr]); + data = qobject_from_jsonf("{ 'device': %s, 'msg': %s, 'offset': %" + PRId64 ", 'size': %" PRId64 " }", bs->device_name, message, + offset, size); + monitor_protocol_event(QEVENT_BLOCK_IMAGE_CORRUPTED, data); + g_free(message); + qobject_decref(data); + + qcow2_mark_corrupt(bs); + bs->drv = NULL; /* make BDS unusable */ + return -EIO; + } + + return 0; +} |