From d4b88a0c0def14366ef18bd6ab18689f0bbd18f7 Mon Sep 17 00:00:00 2001
Message-Id: <d4b88a0c0def14366ef18bd6ab18689f0bbd18f7@dist-git>
From: Peter Krempa <pkrempa@redhat.com>
Date: Fri, 21 Nov 2014 09:53:04 +0100
Subject: [PATCH] storage: qemu: Fix security labelling of new image chain
 elements

When creating a disk image snapshot the libvirt code would blindly copy
the parents label to the newly created image. This runs into problems
when you start a VM from an image hosted on NFS (or other storage system
that doesn't support selinux labels) and the snapshot destination is on
a storage system that does support selinux labels. Libvirt's code in
that case generates a different security label for the image hosted on
NFS. This label is valid only for NFS images and doesn't allow access in
case of a locally stored image.

To fix this issue libvirt needs to refrain from copying security
information in cases where the default domain seclabel is a better
choice.

This patch repurposes the now unused @force argument of
virStorageSourceInitChainElement to denote whether a copy of the
security labelling stuff should be attempted or not. This allows to
fine-control the copy operation for cases where we need to keep the
label of the old disk vs. the cases where we need to keep the label
unset to use the default domain imagelabel.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1151718
(cherry picked from commit 7e130e8b3505ce0f821081dffde8c13a7ff921b3)

Conflicts:
	src/qemu/qemu_driver.c - functional: new block copy api not
                                             backported
	src/util/virstoragefile.c - context: single line block cleanup
                                             not backported

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
---
 src/qemu/qemu_driver.c    |  2 +-
 src/qemu/qemu_process.c   |  2 +-
 src/util/virstoragefile.c | 17 +++++++----------
 3 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 8e6ef1e..5d2a335 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -16064,7 +16064,7 @@ qemuDomainBlockCommit(virDomainPtr dom,
             goto endjob;
         if (virStorageSourceInitChainElement(mirror,
                                              disk->src,
-                                             false) < 0)
+                                             true) < 0)
             goto endjob;
     }
 
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index d6e10e3..fa8b7f8 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -1063,7 +1063,7 @@ qemuProcessHandleBlockJob(qemuMonitorPtr mon ATTRIBUTE_UNUSED,
                         copy = virStorageSourceCopy(disk->mirror, false);
                         if (virStorageSourceInitChainElement(copy,
                                                              persistDisk->src,
-                                                             false) < 0) {
+                                                             true) < 0) {
                             VIR_WARN("Unable to update persistent definition "
                                      "on vm %s after block job",
                                      vm->def->name);
diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
index 6e6ee08..d58f9ed 100644
--- a/src/util/virstoragefile.c
+++ b/src/util/virstoragefile.c
@@ -1894,29 +1894,26 @@ virStorageSourceCopy(const virStorageSource *src,
  * virStorageSourceInitChainElement:
  * @newelem: New backing chain element disk source
  * @old: Existing top level disk source
- * @force: Force-copy the information
+ * @transferLabels: Transfer security lables.
  *
  * Transfers relevant information from the existing disk source to the new
  * backing chain element if they weren't supplied so that labelling info
  * and possibly other stuff is correct.
  *
- * If @force is true, user-supplied information for the new backing store
- * element is overwritten from @old instead of keeping it.
+ * If @transferLabels is true, security labels from the existing disk are copied
+ * to the new disk. Otherwise the default domain imagelabel label will be used.
  *
  * Returns 0 on success, -1 on error.
  */
 int
 virStorageSourceInitChainElement(virStorageSourcePtr newelem,
                                  virStorageSourcePtr old,
-                                 bool force)
+                                 bool transferLabels)
 {
     int ret = -1;
 
-    if (force) {
-        virStorageSourceSeclabelsClear(newelem);
-    }
-
-    if (!newelem->seclabels &&
+    if (transferLabels &&
+        !newelem->seclabels &&
         virStorageSourceSeclabelsCopy(newelem, old) < 0)
         goto cleanup;
 
@@ -2347,7 +2344,7 @@ virStorageSourceNewFromBacking(virStorageSourcePtr parent)
         }
 
         /* copy parent's labelling and other top level stuff */
-        if (virStorageSourceInitChainElement(ret, parent, false) < 0)
+        if (virStorageSourceInitChainElement(ret, parent, true) < 0)
             goto error;
     }
 
-- 
2.1.3