From f24423bd902bce29bc546cf8d030bfa369726ab1 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Fri, 20 Apr 2012 15:50:39 +0200 Subject: qcow2: Fix refcount block allocation during qcow2_alloc_cluster_at() Refcount block allocation and refcount table growth rely on s->free_cluster_index pointing to somewhere after the current allocation. Change qcow2_alloc_cluster_at() to fulfill this assumption. Without this change it could happen that a newly allocated refcount block and the allocated data block point to the same area in the image file, causing data corruption in the long run. This fixes a bug that became first visible after commit 250196f1. Signed-off-by: Kevin Wolf --- block/qcow2-refcount.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'block') diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 565bd54902..6c383373de 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -587,6 +587,7 @@ int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset, { BDRVQcowState *s = bs->opaque; uint64_t cluster_index; + uint64_t old_free_cluster_index; int i, refcount, ret; /* Check how many clusters there are free */ @@ -602,11 +603,16 @@ int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset, } /* And then allocate them */ + old_free_cluster_index = s->free_cluster_index; + s->free_cluster_index = cluster_index + i; + ret = update_refcount(bs, offset, i << s->cluster_bits, 1); if (ret < 0) { return ret; } + s->free_cluster_index = old_free_cluster_index; + return i; } -- cgit v1.2.3