[libvirt] [PATCH 3/8] storage: Prior to creating a volume, refresh the pool
Michal Privoznik
mprivozn at redhat.com
Mon Oct 5 11:28:14 UTC 2015
On 02.10.2015 15:41, John Ferlan wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1233003
>
> Although perhaps bordering on a don't do that type scenario, if
> someone creates a volume in a pool outside of libvirt, then uses that
> same name to create a volume in the pool via libvirt, then the creation
> will fail and in some cases cause the same name volume to be deleted.
>
> This patch will refresh the pool just prior to checking whether the
> named volume exists prior to creating the volume in the pool. While
> it's still possible to have a timing window to create a file after the
> check - at least we tried. At that point, someone is being malicious.
>
> Signed-off-by: John Ferlan <jferlan at redhat.com>
> ---
> src/storage/storage_driver.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/src/storage/storage_driver.c b/src/storage/storage_driver.c
> index 7aaa060..ddf4405 100644
> --- a/src/storage/storage_driver.c
> +++ b/src/storage/storage_driver.c
> @@ -1796,6 +1796,15 @@ storageVolCreateXML(virStoragePoolPtr obj,
> if (virStorageVolCreateXMLEnsureACL(obj->conn, pool->def, voldef) < 0)
> goto cleanup;
>
> + /* While not perfect, refresh the list of volumes in the pool and
> + * then check that the incoming name isn't already in the pool.
> + */
> + if (backend->refreshPool) {
> + virStoragePoolObjClearVols(pool);
> + if (backend->refreshPool(obj->conn, pool) < 0)
> + goto cleanup;
> + }
> +
> if (virStorageVolDefFindByName(pool, voldef->name)) {
> virReportError(VIR_ERR_STORAGE_VOL_EXIST,
> _("'%s'"), voldef->name);
>
Okay, this makes sense. Not only from the POV you are presenting, but I'd expect my pool to be refreshed after I create new volume in it.
And I think we have a way to eliminate even the little window - just track if we successfully built the volume or not. Something among these lines:
diff --git a/src/storage/storage_driver.c b/src/storage/storage_driver.c
index ddf4405..dd28f3f 100644
--- a/src/storage/storage_driver.c
+++ b/src/storage/storage_driver.c
@@ -1857,7 +1857,7 @@ storageVolCreateXML(virStoragePoolPtr obj,
voldef->building = true;
virStoragePoolObjUnlock(pool);
- buildret = backend->buildVol(obj->conn, pool, buildvoldef, flags);
+ buildret = backend->buildVol(obj->conn, pool, buildvoldef, &created, flags);
storageDriverLock();
virStoragePoolObjLock(pool);
@@ -1866,7 +1866,7 @@ storageVolCreateXML(virStoragePoolPtr obj,
voldef->building = false;
pool->asyncjobs--;
- if (buildret < 0) {
+ if (buildret < 0 && created) {
VIR_FREE(buildvoldef);
storageVolDeleteInternal(volobj, backend, pool, voldef,
0, false);
At any rate, ACK to this patch as is.
Michal
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