From f8413b3c23b08a547ce18609acc6fae5fd04ed5c Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 4 Dec 2013 11:06:36 +0100 Subject: [PATCH] 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: Kevin Wolf Reviewed-by: Fam Zheng Reviewed-by: Paolo Bonzini Signed-off-by: Stefan Hajnoczi --- block/qcow2.c | 36 ++++++++++++++++++++---------------- 1 file changed, 20 insertions(+), 16 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index 19e037406c..f29aa88671 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -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; -- GitLab