Il 26/11/2013 11:48, Kevin Wolf ha scritto:
> Strictly speaking, this is only required for has_zero_init() == false,
> but it's easy enough to just do a cluster-aligned write that is padded
> with zeros after the header.
>
> This fixes that after 'qemu-img create' header extensions are attempted
> to be parsed that are really just random leftover data.
>
> Cc: qemu-sta...@nongnu.org
> Signed-off-by: Kevin Wolf <kw...@redhat.com>
Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> block/qcow2.c | 37 +++++++++++++++++++++----------------
> 1 file changed, 21 insertions(+), 16 deletions(-)
>
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 6e5d98d..7c18587 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -1471,7 +1471,7 @@ static int qcow2_create2(const char *filename, int64_t
> total_size,
> * size for any qcow2 image.
> */
> BlockDriverState* bs;
> - QCowHeader header;
> + QCowHeader *header;
> uint8_t* refcount_table;
> Error *local_err = NULL;
> int ret;
> @@ -1489,30 +1489,35 @@ static int qcow2_create2(const char *filename,
> int64_t total_size,
> }
>
> /* Write the header */
> - memset(&header, 0, sizeof(header));
> - header.magic = cpu_to_be32(QCOW_MAGIC);
> - header.version = cpu_to_be32(version);
> - header.cluster_bits = cpu_to_be32(cluster_bits);
> - header.size = cpu_to_be64(0);
> - header.l1_table_offset = cpu_to_be64(0);
> - header.l1_size = cpu_to_be32(0);
> - header.refcount_table_offset = cpu_to_be64(cluster_size);
> - header.refcount_table_clusters = cpu_to_be32(1);
> - header.refcount_order = cpu_to_be32(3 + REFCOUNT_SHIFT);
> - header.header_length = cpu_to_be32(sizeof(header));
> + QEMU_BUILD_BUG_ON((1 << MIN_CLUSTER_BITS) < sizeof(*header));
> + header = g_malloc(cluster_size);
> + memset(header, 0, cluster_size);
> + *header = (QCowHeader) {
> + .magic = cpu_to_be32(QCOW_MAGIC),
> + .version = cpu_to_be32(version),
> + .cluster_bits = cpu_to_be32(cluster_bits),
> + .size = cpu_to_be64(0),
> + .l1_table_offset = cpu_to_be64(0),
> + .l1_size = cpu_to_be32(0),
> + .refcount_table_offset = cpu_to_be64(cluster_size),
> + .refcount_table_clusters = cpu_to_be32(1),
> + .refcount_order = cpu_to_be32(3 + REFCOUNT_SHIFT),
> + .header_length = cpu_to_be32(sizeof(*header)),
> + };
>
> if (flags & BLOCK_FLAG_ENCRYPT) {
> - header.crypt_method = cpu_to_be32(QCOW_CRYPT_AES);
> + header->crypt_method = cpu_to_be32(QCOW_CRYPT_AES);
> } else {
> - header.crypt_method = cpu_to_be32(QCOW_CRYPT_NONE);
> + header->crypt_method = cpu_to_be32(QCOW_CRYPT_NONE);
> }
>
> if (flags & BLOCK_FLAG_LAZY_REFCOUNTS) {
> - header.compatible_features |=
> + header->compatible_features |=
> cpu_to_be64(QCOW2_COMPAT_LAZY_REFCOUNTS);
> }
>
> - ret = bdrv_pwrite(bs, 0, &header, sizeof(header));
> + ret = bdrv_pwrite(bs, 0, header, cluster_size);
> + g_free(header);
> if (ret < 0) {
> error_setg_errno(errp, -ret, "Could not write qcow2 header");
> goto out;
>
