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qcow2: fix possible corruption when reading multiple clusters

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if multiple sectors spanning multiple clusters are read the
function count_contiguous_clusters should ensure that the
cluster type should not change between the clusters.

Especially the for-loop should break when we have one
or more normal clusters followed by a compressed cluster.

Unfortunately the wrong macro was used in the mask to
compare the flags.

This was discovered while debugging a data corruption
issue when converting a compressed qcow2 image to raw.
qemu-img reads 2MB chunks which span multiple clusters.

CC: qemu-stable@nongnu.org
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Peter Lieven 2013-11-12 13:48:07 +01:00 committed by Kevin Wolf
parent 968854c8a1
commit 78a52ad5ac
1 changed files with 1 additions and 1 deletions
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2
block/qcow2-cluster.c
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@ -290,7 +290,7 @@ static int count_contiguous_clusters(uint64_t nb_clusters, int cluster_size,
uint64_t *l2_table, uint64_t stop_flags)
{
int i;
uint64_t mask = stop_flags | L2E_OFFSET_MASK | QCOW2_CLUSTER_COMPRESSED;
uint64_t mask = stop_flags | L2E_OFFSET_MASK | QCOW_OFLAG_COMPRESSED;
uint64_t first_entry = be64_to_cpu(l2_table[0]);
uint64_t offset = first_entry & mask;