[libvirt] [PATCH] conf: RNG: Always fill in default random source path for default backend

[Peter Krempa]

Libvirt documents that the default entropy source for the 'random'
backend of a RNG device is /dev/random. Instead of storing and
propagating NULL across our code and checking it in multiple places fill
the default in the post parse callback and use that in the other places.
---
Sending the fix as promised in the multiple-rng series.


 src/conf/domain_audit.c                                    | 10 ++--------
 src/conf/domain_conf.c                                     | 14 +++++++++-----
 src/qemu/qemu_cgroup.c                                     | 12 ++++--------
 src/qemu/qemu_command.c                                    |  5 ++---
 .../qemuxml2argvdata/qemuxml2argv-virtio-rng-default.args  |  2 +-
 .../qemuxml2argvdata/qemuxml2argv-virtio-rng-multiple.args |  3 ++-
 6 files changed, 20 insertions(+), 26 deletions(-)

diff --git a/src/conf/domain_audit.c b/src/conf/domain_audit.c
index 2d1b1fb..93625fc 100644
--- a/src/conf/domain_audit.c
+++ b/src/conf/domain_audit.c
@@ -253,10 +253,7 @@ virDomainAuditRNG(virDomainObjPtr vm,
     if (newDef) {
         switch ((virDomainRNGBackend) newDef->backend) {
         case VIR_DOMAIN_RNG_BACKEND_RANDOM:
-            if (newDef->source.file)
-                newsrcpath = newDef->source.file;
-            else
-                newsrcpath = "/dev/random";
+            newsrcpath = newDef->source.file;
             break;

         case VIR_DOMAIN_RNG_BACKEND_EGD:
@@ -271,10 +268,7 @@ virDomainAuditRNG(virDomainObjPtr vm,
     if (oldDef) {
         switch ((virDomainRNGBackend) oldDef->backend) {
         case VIR_DOMAIN_RNG_BACKEND_RANDOM:
-            if (oldDef->source.file)
-                oldsrcpath = oldDef->source.file;
-            else
-                oldsrcpath = "/dev/random";
+            oldsrcpath = oldDef->source.file;
             break;

         case VIR_DOMAIN_RNG_BACKEND_EGD:
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 9c3cd8a..910f6e2 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -3057,6 +3057,14 @@ virDomainDeviceDefPostParseInternal(virDomainDeviceDefPtr dev,
         }
     }

+    /* set default path for virtio-rng "random" backend to /dev/random */
+    if (dev->type == VIR_DOMAIN_DEVICE_RNG &&
+        dev->data.rng->backend == VIR_DOMAIN_RNG_BACKEND_RANDOM &&
+        !dev->data.rng->source.file) {
+        if (VIR_STRDUP(dev->data.rng->source.file, "/dev/random") < 0)
+            return -1;
+    }
+
     return 0;
 }

@@ -16546,11 +16554,7 @@ virDomainRNGDefFormat(virBufferPtr buf,

     switch ((virDomainRNGBackend) def->backend) {
     case VIR_DOMAIN_RNG_BACKEND_RANDOM:
-        if (def->source.file)
-            virBufferEscapeString(buf, ">%s</backend>\n", def->source.file);
-        else
-            virBufferAddLit(buf, "/>\n");
-
+        virBufferEscapeString(buf, ">%s</backend>\n", def->source.file);
         break;

     case VIR_DOMAIN_RNG_BACKEND_EGD:
diff --git a/src/qemu/qemu_cgroup.c b/src/qemu/qemu_cgroup.c
index 419be9a..43d14d4 100644
--- a/src/qemu/qemu_cgroup.c
+++ b/src/qemu/qemu_cgroup.c
@@ -587,16 +587,12 @@ qemuSetupDevicesCgroup(virQEMUDriverPtr driver,
     for (i = 0; i < vm->def->nrngs; i++) {
         if (vm->def->rngs[i]->backend == VIR_DOMAIN_RNG_BACKEND_RANDOM) {
             VIR_DEBUG("Setting Cgroup ACL for RNG device");
-            const char *rngpath = vm->def->rngs[i]->source.file;
-
-            /* fix path when using the default */
-            if (!rngpath)
-                rngpath = "/dev/random";
-
-            rv = virCgroupAllowDevicePath(priv->cgroup, rngpath,
+            rv = virCgroupAllowDevicePath(priv->cgroup,
+                                          vm->def->rngs[i]->source.file,
                                           VIR_CGROUP_DEVICE_RW);
             virDomainAuditCgroupPath(vm, priv->cgroup, "allow",
-                                     rngpath, "rw", rv == 0);
+                                     vm->def->rngs[i]->source.file,
+                                     "rw", rv == 0);
             if (rv < 0 &&
                 !virLastErrorIsSystemErrno(ENOENT))
                 goto cleanup;
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 7f9357c..cdf7740 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -5626,9 +5626,8 @@ qemuBuildRNGBackendArgs(virCommandPtr cmd,
             goto cleanup;
         }

-        virBufferAsprintf(&buf, "rng-random,id=%s", dev->info.alias);
-        if (dev->source.file)
-            virBufferAsprintf(&buf, ",filename=%s", dev->source.file);
+        virBufferAsprintf(&buf, "rng-random,id=%s,filename=%s",
+                          dev->info.alias, dev->source.file);

         virCommandAddArg(cmd, "-object");
         virCommandAddArgBuffer(cmd, &buf);
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-default.args b/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-default.args
index 4ae6257..58cc473 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-default.args
+++ b/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-default.args
@@ -3,5 +3,5 @@ LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=none \
 -S -M pc -m 214 -smp 1 -nographic -nodefaults \
 -monitor unix:/tmp/test-monitor,server,nowait -no-acpi -boot c -usb \
 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 \
--object rng-random,id=rng0 \
+-object rng-random,id=rng0,filename=/dev/random \
 -device virtio-rng-pci,rng=rng0,bus=pci.0,addr=0x7
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-multiple.args b/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-multiple.args
index 1082ede..d1faf09 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-multiple.args
+++ b/tests/qemuxml2argvdata/qemuxml2argv-virtio-rng-multiple.args
@@ -3,7 +3,8 @@ LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=none \
 -M pc -m 214 -smp 1 -nographic -nodefaults \
 -monitor unix:/tmp/test-monitor,server,nowait -no-acpi -boot c -usb \
 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 \
--object rng-random,id=rng0 -device virtio-rng-pci,rng=rng0,bus=pci.0,addr=0x7 \
+-object rng-random,id=rng0,filename=/dev/random \
+-device virtio-rng-pci,rng=rng0,bus=pci.0,addr=0x7 \
 -chardev socket,id=charrng1,host=1.2.3.4,port=1234 \
 -object rng-egd,chardev=charrng1,id=rng1 \
 -device virtio-rng-pci,rng=rng1,bus=pci.0,addr=0x4
-- 
2.0.0