Re: [libvirt] [PATCH] snapshot: Don't hose list on deletion failure

If qemuDomainSnapshotDiscard() fails for any reason (rare, but possible with an ill-timed ENOMEM or if qemuDomainSnapshotForEachQcow2() has problems talking to the qemu guest monitor), then an attempt to retry the snapshot deletion API will crash because we didn't undo the effects of virDomainSnapshotDropParent() temporarily rearranging the internal list structures, and the second attempt to drop parents will dereference NULL. Fix it by instead only rearranging the internal list on success. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- Found by accident, since I copied this code to my checkpoint code and hit the segfault there. This one has been latent for years, but is not a security bug since there is no escalation if you already have sufficient privilege to delete snapshots. src/qemu/qemu_driver.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 3f143e91c1..9a3f2a090d 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -16699,8 +16699,9 @@ qemuDomainSnapshotDelete(virDomainSnapshotPtr snapshot, snap->first_child = NULL; ret = 0; } else { - virDomainSnapshotDropParent(snap); ret = qemuDomainSnapshotDiscard(driver, vm, snap, true, metadata_only); + if (ret == 0) + virDomainSnapshotDropParent(snap);