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[Qemu-devel] [PATCH 1/2] qcow2: Undo leaked allocations in co_writev
From: |
Max Reitz |
Subject: |
[Qemu-devel] [PATCH 1/2] qcow2: Undo leaked allocations in co_writev |
Date: |
Thu, 10 Oct 2013 10:52:23 +0200 |
If the write request spans more than one L2 table,
qcow2_alloc_cluster_offset cannot handle the required allocations
atomically. This results in leaks if it allocated new clusters in any
but the last L2 table touched and an error occurs in qcow2_co_writev
before having established the L2 link. These non-atomic allocations
were, however, indeed successful and are therefore given to the caller
in the L2Meta list.
If an error occurs in qcow2_co_writev and the L2Meta list is unwound,
all its remaining entries are clusters whose L2 links were not yet
established. Thus, all allocations in that list should be undone.
Signed-off-by: Max Reitz <address@hidden>
---
block/qcow2.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/block/qcow2.c b/block/qcow2.c
index b2489fb..6bedd5d 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1017,6 +1017,13 @@ fail:
while (l2meta != NULL) {
QCowL2Meta *next;
+ /* Undo all leaked allocations */
+ if (l2meta->nb_clusters != 0) {
+ qcow2_free_clusters(bs, l2meta->alloc_offset,
+ l2meta->nb_clusters << s->cluster_bits,
+ QCOW2_DISCARD_ALWAYS);
+ }
+
if (l2meta->nb_clusters != 0) {
QLIST_REMOVE(l2meta, next_in_flight);
}
--
1.8.3.1
[Qemu-devel] [PATCH 2/2] qemu-iotests: Extend test 026, Max Reitz, 2013/10/10