kvm tools: check the cluster boundary in the qcow read code
The QCOW1 code should always read the data in cluster size. A new function
qcow1_read_cluster() is added to read a cluster wort of data. The current
function to read the data i.e. qcow1_read_sector is modified to use this newly
added function and preserve the cluster boundary.
Signed-off-by: Prasad Joshi <prasadjoshi124@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
diff --git a/qcow.c b/qcow.c
index c426bd3..e5eb12c 100644
--- a/qcow.c
+++ b/qcow.c
@@ -36,68 +36,96 @@
return offset & ((1 << header->cluster_bits)-1);
}
-static int qcow1_read_sector(struct disk_image *self, uint64_t sector, void *dst, uint32_t dst_len)
+static u32 qcow1_read_cluster(struct qcow *q, u64 offset, void *dst,
+ u32 dst_len)
{
- struct qcow *q = self->priv;
struct qcow1_header *header = q->header;
+ struct qcow_table *table = &q->table;
u64 l2_table_offset;
u64 l2_table_size;
+ u64 cluster_size;
u64 clust_offset;
u64 clust_start;
u64 *l2_table = NULL;
u64 l1_idx;
u64 l2_idx;
- u64 offset;
+ u32 length;
- offset = sector << SECTOR_SHIFT;
- if (offset >= header->size)
+ length = cluster_size = 1 << header->cluster_bits;
+
+ l1_idx = get_l1_index(q, offset);
+ if (l1_idx >= table->table_size)
goto out_error;
- l1_idx = get_l1_index(q, offset);
-
- if (l1_idx >= q->table.table_size)
+ clust_offset = get_cluster_offset(q, offset);
+ if (clust_offset >= cluster_size)
goto out_error;
- l2_table_offset = q->table.l1_table[l1_idx];
+ length = cluster_size - clust_offset;
+ if (length > dst_len)
+ length = dst_len;
+
+ l2_table_offset = table->l1_table[l1_idx];
if (!l2_table_offset)
- goto zero_sector;
+ goto zero_cluster;
- l2_table_size = 1 << header->l2_bits;
-
- l2_table = calloc(l2_table_size, sizeof(u64));
+ l2_table_size = 1 << header->l2_bits;
+ l2_table = calloc(l2_table_size, sizeof(u64));
if (!l2_table)
goto out_error;
- if (pread_in_full(q->fd, l2_table, sizeof(u64) * l2_table_size, l2_table_offset) < 0)
+ if (pread_in_full(q->fd, l2_table, l2_table_size * sizeof(u64),
+ l2_table_offset) < 0)
goto out_error;
- l2_idx = get_l2_index(q, offset);
-
+ l2_idx = get_l2_index(q, offset);
if (l2_idx >= l2_table_size)
goto out_error;
- clust_start = be64_to_cpu(l2_table[l2_idx]);
-
+ clust_start = be64_to_cpu(l2_table[l2_idx]);
free(l2_table);
-
if (!clust_start)
- goto zero_sector;
+ goto zero_cluster;
- clust_offset = get_cluster_offset(q, offset);
-
- if (pread_in_full(q->fd, dst, dst_len, clust_start + clust_offset) < 0)
+ if (pread_in_full(q->fd, dst, length, clust_start + clust_offset) < 0)
goto out_error;
- return 0;
-
-zero_sector:
- memset(dst, 0, dst_len);
-
- return 0;
+ return length;
+zero_cluster:
+ memset(dst, 0, length);
+ return length;
out_error:
free(l2_table);
+ return -1;
+}
+static int qcow1_read_sector(struct disk_image *self, uint64_t sector,
+ void *dst, uint32_t dst_len)
+{
+ struct qcow *q = self->priv;
+ struct qcow1_header *header = q->header;
+ char *buf = dst;
+ u64 offset;
+ u32 length;
+ u32 nr;
+
+ length = 0;
+ while (length < dst_len) {
+ offset = sector << SECTOR_SHIFT;
+ if (offset >= header->size)
+ goto out_error;
+
+ nr = qcow1_read_cluster(q, offset, buf, dst_len - length);
+ if (!nr)
+ goto out_error;
+
+ length += nr;
+ buf += nr;
+ sector += (nr >> SECTOR_SHIFT);
+ }
+ return 0;
+out_error:
return -1;
}
