[libvirt] [PATCH v2 8/8] qemu: support use of virtlogd with file based chardevs

[Daniel P. Berrange]

Currently the file based character devices let QEMU write
directly to a file on disk. This allows a malicious QEMU
to inflict a denial of service by consuming all free space.

Switch QEMU to use a pipe to virtlogd, which will enforce
file rollover.

Signed-off-by: Daniel P. Berrange <berrange at redhat.com>
---
 src/qemu/qemu_command.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index e04e55e..462a019 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -3983,18 +3983,19 @@ qemuBuildChrChardevStr(virLogManagerPtr logManager,
         break;
 
     case VIR_DOMAIN_CHR_TYPE_FILE:
-        virBufferAsprintf(&buf, "file,id=char%s,path=%s", alias,
-                          dev->data.file.path);
-        if (dev->data.file.append != VIR_TRISTATE_SWITCH_ABSENT) {
-            if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_CHARDEV_FILE_APPEND)) {
-                virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                               _("append not supported in this QEMU binary"));
-                goto error;
-            }
+        virBufferAsprintf(&buf, "file,id=char%s", alias);
 
-            virBufferAsprintf(&buf, ",append=%s",
-                              virTristateSwitchTypeToString(dev->data.file.append));
+        if (dev->data.file.append != VIR_TRISTATE_SWITCH_ABSENT &&
+            !virQEMUCapsGet(qemuCaps, QEMU_CAPS_CHARDEV_FILE_APPEND)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("append not supported in this QEMU binary"));
+            goto error;
         }
+        if (qemuBuildChrChardevFileStr(virQEMUCapsGet(qemuCaps, QEMU_CAPS_CHARDEV_FILE_APPEND) ?
+                                       logManager : NULL, cmd, def, &buf,
+                                       "file", dev->data.file.path,
+                                       "append", dev->data.file.append) < 0)
+            goto error;
         break;
 
     case VIR_DOMAIN_CHR_TYPE_PIPE:
-- 
2.5.0