1 files changed, 29 insertions, 15 deletions

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 8982b7b762..1947f13a2d 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -124,12 +124,11 @@ int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
 #endif
 
     new_l1_size2 = sizeof(uint64_t) * new_l1_size;
-    new_l1_table = qemu_try_blockalign(bs->file->bs,
-                                       ROUND_UP(new_l1_size2, 512));
+    new_l1_table = qemu_try_blockalign(bs->file->bs, new_l1_size2);
     if (new_l1_table == NULL) {
         return -ENOMEM;
     }
-    memset(new_l1_table, 0, ROUND_UP(new_l1_size2, 512));
+    memset(new_l1_table, 0, new_l1_size2);
 
     if (s->l1_size) {
         memcpy(new_l1_table, s->l1_table, s->l1_size * sizeof(uint64_t));
@@ -217,26 +216,31 @@ static int l2_load(BlockDriverState *bs, uint64_t offset,
 }
 
 /*
- * Writes one sector of the L1 table to the disk (can't update single entries
- * and we really don't want bdrv_pread to perform a read-modify-write)
+ * Writes an L1 entry to disk (note that depending on the alignment
+ * requirements this function may write more that just one entry in
+ * order to prevent bdrv_pwrite from performing a read-modify-write)
  */
-#define L1_ENTRIES_PER_SECTOR (512 / 8)
 int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index)
 {
     BDRVQcow2State *s = bs->opaque;
-    uint64_t buf[L1_ENTRIES_PER_SECTOR] = { 0 };
     int l1_start_index;
     int i, ret;
+    int bufsize = MAX(sizeof(uint64_t),
+                      MIN(bs->file->bs->bl.request_alignment, s->cluster_size));
+    int nentries = bufsize / sizeof(uint64_t);
+    g_autofree uint64_t *buf = g_try_new0(uint64_t, nentries);
 
-    l1_start_index = l1_index & ~(L1_ENTRIES_PER_SECTOR - 1);
-    for (i = 0; i < L1_ENTRIES_PER_SECTOR && l1_start_index + i < s->l1_size;
-         i++)
-    {
+    if (buf == NULL) {
+        return -ENOMEM;
+    }
+
+    l1_start_index = QEMU_ALIGN_DOWN(l1_index, nentries);
+    for (i = 0; i < MIN(nentries, s->l1_size - l1_start_index); i++) {
         buf[i] = cpu_to_be64(s->l1_table[l1_start_index + i]);
     }
 
     ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1,
-            s->l1_table_offset + 8 * l1_start_index, sizeof(buf), false);
+            s->l1_table_offset + 8 * l1_start_index, bufsize, false);
     if (ret < 0) {
         return ret;
     }
@@ -244,7 +248,7 @@ int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index)
     BLKDBG_EVENT(bs->file, BLKDBG_L1_UPDATE);
     ret = bdrv_pwrite_sync(bs->file,
                            s->l1_table_offset + 8 * l1_start_index,
-                           buf, sizeof(buf));
+                           buf, bufsize);
     if (ret < 0) {
         return ret;
     }
@@ -777,6 +781,10 @@ int qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
         (cluster_offset + compressed_size - 1) / QCOW2_COMPRESSED_SECTOR_SIZE -
         (cluster_offset / QCOW2_COMPRESSED_SECTOR_SIZE);
 
+    /* The offset and size must fit in their fields of the L2 table entry */
+    assert((cluster_offset & s->cluster_offset_mask) == cluster_offset);
+    assert((nb_csectors & s->csize_mask) == nb_csectors);
+
     cluster_offset |= QCOW_OFLAG_COMPRESSED |
                       ((uint64_t)nb_csectors << s->csize_shift);
 
@@ -972,6 +980,7 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
 
     assert(l2_index + m->nb_clusters <= s->l2_slice_size);
     for (i = 0; i < m->nb_clusters; i++) {
+        uint64_t offset = cluster_offset + (i << s->cluster_bits);
         /* if two concurrent writes happen to the same unallocated cluster
          * each write allocates separate cluster and writes data concurrently.
          * The first one to complete updates l2 table with pointer to its
@@ -982,8 +991,10 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
             old_cluster[j++] = l2_slice[l2_index + i];
         }
 
-        l2_slice[l2_index + i] = cpu_to_be64((cluster_offset +
-                    (i << s->cluster_bits)) | QCOW_OFLAG_COPIED);
+        /* The offset must fit in the offset field of the L2 table entry */
+        assert((offset & L2E_OFFSET_MASK) == offset);
+
+        l2_slice[l2_index + i] = cpu_to_be64(offset | QCOW_OFLAG_COPIED);
      }
 
 
@@ -1913,6 +1924,9 @@ static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table,
                         goto fail;
                     }
 
+                    /* The offset must fit in the offset field */
+                    assert((offset & L2E_OFFSET_MASK) == offset);
+
                     if (l2_refcount > 1) {
                         /* For shared L2 tables, set the refcount accordingly
                          * (it is already 1 and needs to be l2_refcount) */