qemu: domain: Prevent overflows in memory alignment code

Since libvirt for dubious historical reasons stores memory size as
kibibytes, it's possible that the alignments done in the qemu code
overflow the the maximum representable size in bytes. The XML parser
code handles them in bytes in some stages. Prevent this by doing
overflow checks when alinging the size and add a test case.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1260576

src/qemu/qemu_domain.c

@@ -3521,6 +3521,8 @@ qemuDomainGetMemoryModuleSizeAlignment(const virDomainDef *def,
 int
 qemuDomainAlignMemorySizes(virDomainDefPtr def)
 {
+    unsigned long long maxmemkb = virMemoryMaxValue(false) >> 10;
+    unsigned long long maxmemcapped = virMemoryMaxValue(true) >> 10;
     unsigned long long initialmem = 0;
     unsigned long long mem;
     unsigned long long align = qemuDomainGetMemorySizeAlignment(def);
@@ -3531,6 +3533,13 @@ qemuDomainAlignMemorySizes(virDomainDefPtr def)
     for (i = 0; i < ncells; i++) {
         mem = VIR_ROUND_UP(virDomainNumaGetNodeMemorySize(def->numa, i), align);
         initialmem += mem;
+
+        if (mem > maxmemkb) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("memory size of NUMA node '%zu' overflowed after "
+                             "alignment"), i);
+            return -1;
+        }
         virDomainNumaSetNodeMemorySize(def->numa, i, mem);
     }
 
@@ -3539,14 +3548,32 @@ qemuDomainAlignMemorySizes(virDomainDefPtr def)
     if (initialmem == 0)
         initialmem = VIR_ROUND_UP(virDomainDefGetMemoryInitial(def), align);
 
+    if (initialmem > maxmemcapped) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                       _("initial memory size overflowed after alignment"));
+        return -1;
+    }
+
     virDomainDefSetMemoryInitial(def, initialmem);
 
     def->mem.max_memory = VIR_ROUND_UP(def->mem.max_memory, align);
+    if (def->mem.max_memory > maxmemkb) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                       _("maximum memory size overflowed after alignment"));
+        return -1;
+    }
 
     /* Align memory module sizes */
     for (i = 0; i < def->nmems; i++) {
         align = qemuDomainGetMemoryModuleSizeAlignment(def, def->mems[i]);
         def->mems[i]->size = VIR_ROUND_UP(def->mems[i]->size, align);
+
+        if (def->mems[i]->size > maxmemkb) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("size of memory module '%zu' overflowed after "
+                             "alignment"), i);
+            return -1;
+        }
     }
 
     return 0;

tests/qemuxml2argvdata/qemuxml2argv-memory-align-fail.xml

@@ -0,0 +1,29 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <maxMemory slots='16' unit='KiB'>9007199254740991</maxMemory>
+  <memory unit='KiB'>9007199254740991</memory>
+  <currentMemory unit='KiB'>9007199254740991</currentMemory>
+  <vcpu placement='static' cpuset='0-1'>2</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu>
+    <topology sockets='2' cores='1' threads='1'/>
+    <numa>
+      <cell id='0' cpus='0-1' memory='9007199254740991' unit='KiB'/>
+    </numa>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <controller type='ide' index='0'/>
+    <controller type='usb' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -1660,6 +1660,7 @@ mymain(void)
     DO_TEST_PARSE_ERROR("shmem-msi-only", NONE);
     DO_TEST("cpu-host-passthrough-features", QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST);
 
+    DO_TEST_FAILURE("memory-align-fail", NONE);
     DO_TEST_FAILURE("memory-hotplug-nonuma", QEMU_CAPS_DEVICE_PC_DIMM);
     DO_TEST_FAILURE("memory-hotplug", NONE);
     DO_TEST("memory-hotplug", QEMU_CAPS_DEVICE_PC_DIMM, QEMU_CAPS_NUMA);