Commit f8413b3c authored by Kevin Wolf's avatar Kevin Wolf Committed by Stefan Hajnoczi
Browse files

qcow2: Zero-initialise first cluster for new images 



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-stable@nongnu.org
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
Reviewed-by: default avatarFam Zheng <famz@redhat.com>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 66f6b814

block/qcow2.c

+20 −16
Original line number Diff line number Diff line
@@ -1472,7 +1472,7 @@ 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;
@@ -1490,30 +1490,34 @@ 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_malloc0(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;