[libvirt] [PATCH] daemon: avoid memleak when ListAll returns nothing

Eric Blake eblake at redhat.com
Mon Mar 16 16:07:13 UTC 2015


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 at redhat.com>
---

I'm pushing this now, and backporting to stable maintenance
branches, based on review on the libvirt-security list (where
we decided it was not severe enough to need a CVE).  I'll be
sending a Libvirt Security Notice about the issue later.

 daemon/remote.c | 55 ++++++++++++++++++++++---------------------------------
 1 file changed, 22 insertions(+), 33 deletions(-)

diff --git a/daemon/remote.c b/daemon/remote.c
index ff64eeb..fc2237d 100644
--- 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;
 }

@@ -4605,11 +4604,10 @@ 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;
 }

@@ -4674,11 +4672,10 @@ 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;
 }

@@ -4733,11 +4730,10 @@ 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;
 }

@@ -4796,11 +4792,10 @@ 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;
 }
@@ -4856,11 +4851,10 @@ 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;
 }

@@ -4915,11 +4909,10 @@ 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;
 }

@@ -4974,11 +4967,10 @@ 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;
 }

@@ -5033,11 +5025,10 @@ 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;
 }

@@ -5092,11 +5083,10 @@ 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;
 }

@@ -6264,11 +6254,10 @@ 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;
 }
-- 
2.1.0




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