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-rw-r--r--block/parallels.c19
1 files changed, 13 insertions, 6 deletions
diff --git a/block/parallels.c b/block/parallels.c
index 4173b3f..90acf79 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -192,8 +192,7 @@ static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, int *pnum)
{
BDRVParallelsState *s = bs->opaque;
- uint32_t idx, to_allocate, i;
- int64_t pos, space;
+ int64_t pos, space, idx, to_allocate, i;
pos = block_status(s, sector_num, nb_sectors, pnum);
if (pos > 0) {
@@ -201,11 +200,19 @@ static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num,
}
idx = sector_num / s->tracks;
- if (idx >= s->bat_size) {
- return -EINVAL;
- }
-
to_allocate = DIV_ROUND_UP(sector_num + *pnum, s->tracks) - idx;
+
+ /* This function is called only by parallels_co_writev(), which will never
+ * pass a sector_num at or beyond the end of the image (because the block
+ * layer never passes such a sector_num to that function). Therefore, idx
+ * is always below s->bat_size.
+ * block_status() will limit *pnum so that sector_num + *pnum will not
+ * exceed the image end. Therefore, idx + to_allocate cannot exceed
+ * s->bat_size.
+ * Note that s->bat_size is an unsigned int, therefore idx + to_allocate
+ * will always fit into a uint32_t. */
+ assert(idx < s->bat_size && idx + to_allocate <= s->bat_size);
+
space = to_allocate * s->tracks;
if (s->data_end + space > bdrv_getlength(bs->file->bs) >> BDRV_SECTOR_BITS) {
int ret;