Commit message: bochs: Check catalog_size header field (CVE-2014-0143)

It should neither become negative nor allow unbounded memory
allocations. This fixes aborts in g_malloc() and an s->catalog_bitmap
buffer overflow on big endian hosts.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
CVE: CVE-2014-0143
CWE: CWE-190
Vulnerability description: Multiple integer overflows in the block drivers in QEMU, possibly before 2.0.0, allow local users to cause a denial of service (crash) via a crafted catalog size in (1) the parallels_open function in block/parallels.c or (2) bochs_open function in bochs.c, a large L1 table in the (3) qcow2_snapshot_load_tmp in qcow2-snapshot.c or (4) qcow2_grow_l1_table function in qcow2-cluster.c, (5) a large request in the bdrv_check_byte_request function in block.c and other block drivers, (6) crafted cluster indexes in the get_refcount function in qcow2-refcount.c, or (7) a large number of blocks in the cloop_open function in cloop.c, which trigger buffer overflows, memory corruption, large memory allocations and out-of-bounds read and writes.

Project: qemu

static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
                      Error **errp)
{
    BDRVBochsState *s = bs->opaque;
    uint32_t i;
    struct bochs_header bochs;
    int ret;

    bs->read_only = 1; // no write support yet

    ret = bdrv_pread(bs->file, 0, &bochs, sizeof(bochs));
    if (ret < 0) {
        return ret;
    }

    if (strcmp(bochs.magic, HEADER_MAGIC) ||
        strcmp(bochs.type, REDOLOG_TYPE) ||
        strcmp(bochs.subtype, GROWING_TYPE) ||
	((le32_to_cpu(bochs.version) != HEADER_VERSION) &&
	(le32_to_cpu(bochs.version) != HEADER_V1))) {
        error_setg(errp, "Image not in Bochs format");
        return -EINVAL;
    }

    if (le32_to_cpu(bochs.version) == HEADER_V1) {
        bs->total_sectors = le64_to_cpu(bochs.extra.redolog_v1.disk) / 512;
    } else {
         bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
     }
 
    /* Limit to 1M entries to avoid unbounded allocation. This is what is
     * needed for the largest image that bximage can create (~8 TB). */
     s->catalog_size = le32_to_cpu(bochs.catalog);
    if (s->catalog_size > 0x100000) {
        error_setg(errp, "Catalog size is too large");
        return -EFBIG;
    }

     s->catalog_bitmap = g_malloc(s->catalog_size * 4);
 
     ret = bdrv_pread(bs->file, le32_to_cpu(bochs.header), s->catalog_bitmap,

    s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);

    s->bitmap_blocks = 1 + (le32_to_cpu(bochs.bitmap) - 1) / 512;
    s->extent_blocks = 1 + (le32_to_cpu(bochs.extent) - 1) / 512;

    s->extent_size = le32_to_cpu(bochs.extent);

    qemu_co_mutex_init(&s->lock);
    return 0;

fail:
 
     s->extent_size = le32_to_cpu(bochs.extent);
 
    if (s->catalog_size < bs->total_sectors / s->extent_size) {
        error_setg(errp, "Catalog size is too small for this disk size");
        ret = -EINVAL;
        goto fail;
    }

     qemu_co_mutex_init(&s->lock);
     return 0;
    extent_index = offset / s->extent_size;
    extent_offset = (offset % s->extent_size) / 512;

    if (s->catalog_bitmap[extent_index] == 0xffffffff) {
	return -1; /* not allocated */
    }

    bitmap_offset = s->data_offset + (512 * s->catalog_bitmap[extent_index] *
	(s->extent_blocks + s->bitmap_blocks));

    /* read in bitmap for current extent */
    if (bdrv_pread(bs->file, bitmap_offset + (extent_offset / 8),
                   &bitmap_entry, 1) != 1) {
        return -1;
    }

    if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
	return -1; /* not allocated */
    }

    return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
}