[libvirt] [PATCH 2/2] qemu: domain: Prevent overflows in memory alignment code

[Peter Krempa]

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                             | 27 ++++++++++++++++++++
 .../qemuxml2argv-memory-align-fail.xml             | 29 ++++++++++++++++++++++
 tests/qemuxml2argvtest.c                           |  1 +
 3 files changed, 57 insertions(+)
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-memory-align-fail.xml

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index ed21245..a872598 100644
--- a/src/qemu/qemu_domain.c
+++ b/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;
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-memory-align-fail.xml b/tests/qemuxml2argvdata/qemuxml2argv-memory-align-fail.xml
new file mode 100644
index 0000000..bdbdc5b
--- /dev/null
+++ b/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>
diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
index 6513651..37f806e 100644
--- a/tests/qemuxml2argvtest.c
+++ b/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);
-- 
2.6.2