[PATCH v2 5/5] qemu: Use transactions from security driver

[Michal Privoznik <mprivozn@xxxxxxxxxx>]

So far if qemu is spawned under separate mount namespace in order
to relabel everything it needs an access to the security driver
is run in that namespace too. This has a very nasty down side -
it is being run in a separate process, so any internal state
transition is NOT reflected in the dameon. This can lead to many
sleepless nights. Therefore, use the transaction APIs so that
libvirt developers can sleep tight again.

Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
---
 src/qemu/qemu_security.c | 100 ++++++++++++++---------------------------------
 1 file changed, 30 insertions(+), 70 deletions(-)

diff --git a/src/qemu/qemu_security.c b/src/qemu/qemu_security.c
index 9ab91e9f2..544feeb4a 100644
--- a/src/qemu/qemu_security.c
+++ b/src/qemu/qemu_security.c
@@ -40,66 +40,31 @@ struct qemuSecuritySetRestoreAllLabelData {
 };
 
 
-static int
-qemuSecuritySetRestoreAllLabelHelper(pid_t pid,
-                                     void *opaque)
-{
-    struct qemuSecuritySetRestoreAllLabelData *data = opaque;
-
-    virSecurityManagerPostFork(data->driver->securityManager);
-
-    if (data->set) {
-        VIR_DEBUG("Setting up security labels inside namespace pid=%lld",
-                  (long long) pid);
-        if (virSecurityManagerSetAllLabel(data->driver->securityManager,
-                                          data->vm->def,
-                                          data->stdin_path) < 0)
-            return -1;
-    } else {
-        VIR_DEBUG("Restoring security labels inside namespace pid=%lld",
-                  (long long) pid);
-        if (virSecurityManagerRestoreAllLabel(data->driver->securityManager,
-                                              data->vm->def,
-                                              data->migrated) < 0)
-            return -1;
-    }
-
-    return 0;
-}
-
-
 int
 qemuSecuritySetAllLabel(virQEMUDriverPtr driver,
                         virDomainObjPtr vm,
                         const char *stdin_path)
 {
-    struct qemuSecuritySetRestoreAllLabelData data;
+    int ret = -1;
 
-    memset(&data, 0, sizeof(data));
+    if (qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT) &&
+        virSecurityManagerTransactionStart(driver->securityManager) < 0)
+        goto cleanup;
 
-    data.set = true;
-    data.driver = driver;
-    data.vm = vm;
-    data.stdin_path = stdin_path;
+    if (virSecurityManagerSetAllLabel(driver->securityManager,
+                                      vm->def,
+                                      stdin_path) < 0)
+        goto cleanup;
 
-    if (qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT)) {
-        if (virSecurityManagerPreFork(driver->securityManager) < 0)
-            return -1;
-        if (virProcessRunInMountNamespace(vm->pid,
-                                          qemuSecuritySetRestoreAllLabelHelper,
-                                          &data) < 0) {
-            virSecurityManagerPostFork(driver->securityManager);
-            return -1;
-        }
-        virSecurityManagerPostFork(driver->securityManager);
+    if (qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT) &&
+        virSecurityManagerTransactionCommit(driver->securityManager,
+                                            vm->pid) < 0)
+        goto cleanup;
 
-    } else {
-        if (virSecurityManagerSetAllLabel(driver->securityManager,
-                                          vm->def,
-                                          stdin_path) < 0)
-            return -1;
-    }
-    return 0;
+    ret = 0;
+ cleanup:
+    virSecurityManagerTransactionAbort(driver->securityManager);
+    return ret;
 }
 
 
@@ -108,27 +73,22 @@ qemuSecurityRestoreAllLabel(virQEMUDriverPtr driver,
                             virDomainObjPtr vm,
                             bool migrated)
 {
-    struct qemuSecuritySetRestoreAllLabelData data;
+    if (qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT) &&
+        virSecurityManagerTransactionStart(driver->securityManager) < 0)
+        goto cleanup;
 
-    memset(&data, 0, sizeof(data));
-
-    data.driver = driver;
-    data.vm = vm;
-    data.migrated = migrated;
-
-    if (qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT)) {
-        if (virSecurityManagerPreFork(driver->securityManager) < 0)
-            return;
-
-        virProcessRunInMountNamespace(vm->pid,
-                                      qemuSecuritySetRestoreAllLabelHelper,
-                                      &data);
-        virSecurityManagerPostFork(driver->securityManager);
-    } else {
-        virSecurityManagerRestoreAllLabel(driver->securityManager,
+    if (virSecurityManagerRestoreAllLabel(driver->securityManager,
                                           vm->def,
-                                          migrated);
-    }
+                                          migrated) < 0)
+        goto cleanup;
+
+    if (qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT) &&
+        virSecurityManagerTransactionCommit(driver->securityManager,
+                                            vm->pid) < 0)
+        goto cleanup;
+
+ cleanup:
+    virSecurityManagerTransactionAbort(driver->securityManager);
 }
 
 
-- 
2.11.0

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