daemon: avoid memleak when ListAll returns nothing

Commit 4f25146 (v1.2.8) managed to silence Coverity, but at the
cost of a memory leak detected by valgrind:
==24129== 40 bytes in 5 blocks are definitely lost in loss record 355 of 637
==24129==    at 0x4A08B1C: realloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==24129==    by 0x5084B8E: virReallocN (viralloc.c:245)
==24129==    by 0x514D5AA: virDomainObjListExport (domain_conf.c:22200)
==24129==    by 0x201227DB: qemuConnectListAllDomains (qemu_driver.c:18042)
==24129==    by 0x51CC1B6: virConnectListAllDomains (libvirt-domain.c:6797)
==24129==    by 0x14173D: remoteDispatchConnectListAllDomains (remote.c:1580)
==24129==    by 0x121BE1: remoteDispatchConnectListAllDomainsHelper (remote_dispatch.h:1072)

In short, every time a client calls a ListAll variant and asks
for the resulting list, but there are 0 elements to return, we
end up leaking the 1-entry array that holds the NULL terminator.

What's worse, a read-only client can access these functions in a
tight loop to cause libvirtd to eventually run out of memory; and
this can be considered a denial of service attack against more
privileged clients.  Thankfully, the leak is so small (8 bytes per
call) that you would already have some other denial of service with
any guest calling the API that frequently, so an out-of-memory
crash is unlikely enough that this did not warrant a CVE.

* daemon/remote.c (remoteDispatchConnectListAllDomains)
(remoteDispatchDomainListAllSnapshots)
(remoteDispatchDomainSnapshotListAllChildren)
(remoteDispatchConnectListAllStoragePools)
(remoteDispatchStoragePoolListAllVolumes)
(remoteDispatchConnectListAllNetworks)
(remoteDispatchConnectListAllInterfaces)
(remoteDispatchConnectListAllNodeDevices)
(remoteDispatchConnectListAllNWFilters)
(remoteDispatchConnectListAllSecrets)
(remoteDispatchNetworkGetDHCPLeases): Plug leak.

Signed-off-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit 3c2ff5029b83c9b33be0f1607a3c61f4f5850612)

diff --git a/daemon/remote.c b/daemon/remote.c
index d657a09d8a3eb0ae4c0ac9ff6587f68386f5ee9f..9431cc398f92accaef122be39b62ef3ec411c525 100644 (file)
--- a/daemon/remote.c
+++ b/daemon/remote.c
@@ -1609,11 +1609,10 @@ remoteDispatchConnectListAllDomains(virNetServerPtr server ATTRIBUTE_UNUSED,
  cleanup:
     if (rv < 0)
         virNetMessageSaveError(rerr);
-    if (doms && ndomains > 0) {
+    if (doms && ndomains > 0)
         for (i = 0; i < ndomains; i++)
             virObjectUnref(doms[i]);
-        VIR_FREE(doms);
-    }
+    VIR_FREE(doms);
     return rv;
 }
 
@@ -4533,11 +4532,10 @@ remoteDispatchDomainListAllSnapshots(virNetServerPtr server ATTRIBUTE_UNUSED,
     if (rv < 0)
         virNetMessageSaveError(rerr);
     virObjectUnref(dom);
-    if (snaps && nsnaps > 0) {
+    if (snaps && nsnaps > 0)
         for (i = 0; i < nsnaps; i++)
             virObjectUnref(snaps[i]);
-        VIR_FREE(snaps);
-    }
+    VIR_FREE(snaps);
     return rv;
 }
 
@@ -4602,11 +4600,10 @@ remoteDispatchDomainSnapshotListAllChildren(virNetServerPtr server ATTRIBUTE_UNU
         virNetMessageSaveError(rerr);
     virObjectUnref(snapshot);
     virObjectUnref(dom);
-    if (snaps && nsnaps > 0) {
+    if (snaps && nsnaps > 0)
         for (i = 0; i < nsnaps; i++)
             virObjectUnref(snaps[i]);
-        VIR_FREE(snaps);
-    }
+    VIR_FREE(snaps);
     return rv;
 }
 
@@ -4661,11 +4658,10 @@ remoteDispatchConnectListAllStoragePools(virNetServerPtr server ATTRIBUTE_UNUSED
  cleanup:
     if (rv < 0)
         virNetMessageSaveError(rerr);
-    if (pools && npools > 0) {
+    if (pools && npools > 0)
         for (i = 0; i < npools; i++)
             virObjectUnref(pools[i]);
-        VIR_FREE(pools);
-    }
+    VIR_FREE(pools);
     return rv;
 }
 
@@ -4724,11 +4720,10 @@ remoteDispatchStoragePoolListAllVolumes(virNetServerPtr server ATTRIBUTE_UNUSED,
  cleanup:
     if (rv < 0)
         virNetMessageSaveError(rerr);
-    if (vols && nvols > 0) {
+    if (vols && nvols > 0)
         for (i = 0; i < nvols; i++)
             virObjectUnref(vols[i]);
-        VIR_FREE(vols);
-    }
+    VIR_FREE(vols);
     virObjectUnref(pool);
     return rv;
 }
@@ -4784,11 +4779,10 @@ remoteDispatchConnectListAllNetworks(virNetServerPtr server ATTRIBUTE_UNUSED,
  cleanup:
     if (rv < 0)
         virNetMessageSaveError(rerr);
-    if (nets && nnets > 0) {
+    if (nets && nnets > 0)
         for (i = 0; i < nnets; i++)
             virObjectUnref(nets[i]);
-        VIR_FREE(nets);
-    }
+    VIR_FREE(nets);
     return rv;
 }
 
@@ -4843,11 +4837,10 @@ remoteDispatchConnectListAllInterfaces(virNetServerPtr server ATTRIBUTE_UNUSED,
  cleanup:
     if (rv < 0)
         virNetMessageSaveError(rerr);
-    if (ifaces && nifaces > 0) {
+    if (ifaces && nifaces > 0)
         for (i = 0; i < nifaces; i++)
             virObjectUnref(ifaces[i]);
-        VIR_FREE(ifaces);
-    }
+    VIR_FREE(ifaces);
     return rv;
 }
 
@@ -4902,11 +4895,10 @@ remoteDispatchConnectListAllNodeDevices(virNetServerPtr server ATTRIBUTE_UNUSED,
  cleanup:
     if (rv < 0)
         virNetMessageSaveError(rerr);
-    if (devices && ndevices > 0) {
+    if (devices && ndevices > 0)
         for (i = 0; i < ndevices; i++)
             virObjectUnref(devices[i]);
-        VIR_FREE(devices);
-    }
+    VIR_FREE(devices);
     return rv;
 }
 
@@ -4961,11 +4953,10 @@ remoteDispatchConnectListAllNWFilters(virNetServerPtr server ATTRIBUTE_UNUSED,
  cleanup:
     if (rv < 0)
         virNetMessageSaveError(rerr);
-    if (filters && nfilters > 0) {
+    if (filters && nfilters > 0)
         for (i = 0; i < nfilters; i++)
             virObjectUnref(filters[i]);
-        VIR_FREE(filters);
-    }
+    VIR_FREE(filters);
     return rv;
 }
 
@@ -5020,11 +5011,10 @@ remoteDispatchConnectListAllSecrets(virNetServerPtr server ATTRIBUTE_UNUSED,
  cleanup:
     if (rv < 0)
         virNetMessageSaveError(rerr);
-    if (secrets && nsecrets > 0) {
+    if (secrets && nsecrets > 0)
         for (i = 0; i < nsecrets; i++)
             virObjectUnref(secrets[i]);
-        VIR_FREE(secrets);
-    }
+    VIR_FREE(secrets);
     return rv;
 }
 
@@ -6192,11 +6182,10 @@ remoteDispatchNetworkGetDHCPLeases(virNetServerPtr server ATTRIBUTE_UNUSED,
  cleanup:
     if (rv < 0)
         virNetMessageSaveError(rerr);
-    if (leases && nleases > 0) {
+    if (leases && nleases > 0)
         for (i = 0; i < nleases; i++)
             virNetworkDHCPLeaseFree(leases[i]);
-        VIR_FREE(leases);
-    }
+    VIR_FREE(leases);
     virObjectUnref(net);
     return rv;
 }