From 3dac48d4a6875a107fb2febd5cefc3ff1a0e33d8 Mon Sep 17 00:00:00 2001 From: Prasad Joshi Date: Sat, 16 Apr 2011 20:40:25 +0100 Subject: [PATCH] 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 Signed-off-by: Pekka Enberg --- qcow.c | 86 ++++++++++++++++++++++++++++++++++++++-------------------- 1 file changed, 57 insertions(+), 29 deletions(-) diff --git a/qcow.c b/qcow.c index c426bd3..e5eb12c 100644 --- a/qcow.c +++ b/qcow.c @@ -36,68 +36,96 @@ static inline u64 get_cluster_offset(struct qcow *q, u64 offset) 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; }