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qcow2: Use pread for inactive L1 in overlap check 

Currently, qcow2_check_metadata_overlap uses bdrv_read to read inactive
L1 tables from disk. The number of sectors to read is calculated through
a truncating integer division, therefore, if the L1 table size is not a
multiple of the sector size, the final entries will not be read and
their entries in memory remain undefined (from the g_malloc).
Using bdrv_pread fixes this.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2013-10-09 10:42:56 +02:00 committed by Kevin Wolf
parent f252080453
commit 998b959c1e
1 changed files with 3 additions and 4 deletions
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7
block/qcow2-refcount.c
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@ -1719,12 +1719,11 @@ int qcow2_check_metadata_overlap(BlockDriverState *bs, int chk, int64_t offset,
for (i = 0; i < s->nb_snapshots; i++) {
uint64_t l1_ofs = s->snapshots[i].l1_table_offset;
uint32_t l1_sz = s->snapshots[i].l1_size;
uint64_t *l1 = g_malloc(l1_sz * sizeof(uint64_t));
uint64_t l1_sz2 = l1_sz * sizeof(uint64_t);
uint64_t *l1 = g_malloc(l1_sz2);
int ret;
ret = bdrv_read(bs->file, l1_ofs / BDRV_SECTOR_SIZE, (uint8_t *)l1,
l1_sz * sizeof(uint64_t) / BDRV_SECTOR_SIZE);
ret = bdrv_pread(bs->file, l1_ofs, l1, l1_sz2);
if (ret < 0) {
g_free(l1);
return ret;