libxl: fix libvirtd segfault

Commit d72ef888 introduced a bug in the libxl driver that will
segfault libvirtd if libxl reports an error message, e.g. when
attempting to initialize the driver on a non-Xen system.  I
assumed it was valid to pass a NULL logger to libxl_ctx_alloc(),
but that is not the case since any errors associated with the ctx
that are emitted by libxl will dereference the logger and crash
libvirtd.

Errors associated with the libxl driver-wide ctx could be useful
for debugging anyway, so create a 'libxl-driver.log' to capture
these errors.

diff --git a/src/libxl/libxl_conf.h b/src/libxl/libxl_conf.h
index 78133b964cd9ae8f066f50a65e1fd81c049b454d..9d72b722422b1d44004aafde339d97579d543c81 100644 (file)
--- a/src/libxl/libxl_conf.h
+++ b/src/libxl/libxl_conf.h
@@ -57,6 +57,9 @@ struct _libxlDriverPrivate {
     virDomainXMLOptionPtr xmlopt;
     unsigned int version;
 
+    /* log stream for driver-wide libxl ctx */
+    FILE *logger_file;
+    xentoollog_logger *logger;
     /* libxl ctx for driver wide ops; getVersion, getNodeInfo, ... */
     libxl_ctx *ctx;
 

diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
index cc9e7724ced31d5718fb141ff34dc8d7b0732960..9dc72617c06a80ae789b5349f0e5aeee12859dc2 100644 (file)
--- a/src/libxl/libxl_driver.c
+++ b/src/libxl/libxl_driver.c
@@ -1180,6 +1180,9 @@ libxlStateCleanup(void)
     virObjectUnref(libxl_driver->xmlopt);
     virObjectUnref(libxl_driver->domains);
     libxl_ctx_free(libxl_driver->ctx);
+    xtl_logger_destroy(libxl_driver->logger);
+    if (libxl_driver->logger_file)
+        VIR_FORCE_FCLOSE(libxl_driver->logger_file);
 
     virObjectUnref(libxl_driver->reservedVNCPorts);
 
@@ -1229,6 +1232,7 @@ libxlStateInitialize(bool privileged,
                      void *opaque ATTRIBUTE_UNUSED)
 {
     const libxl_version_info *ver_info;
+    char *log_file = NULL;
     virCommandPtr cmd;
     int status, ret = 0;
     unsigned int free_mem;
@@ -1308,6 +1312,17 @@ libxlStateInitialize(bool privileged,
         goto error;
     }
 
+    if (virAsprintf(&log_file, "%s/libxl-driver.log", libxl_driver->logDir) < 0)
+        goto error;
+
+    if ((libxl_driver->logger_file = fopen(log_file, "a")) == NULL)  {
+        virReportSystemError(errno,
+                             _("failed to create logfile %s"),
+                             log_file);
+        goto error;
+    }
+    VIR_FREE(log_file);
+
     /* read the host sysinfo */
     if (privileged)
         libxl_driver->hostsysinfo = virSysinfoRead();
@@ -1316,8 +1331,18 @@ libxlStateInitialize(bool privileged,
     if (!libxl_driver->domainEventState)
         goto error;
 
-    if (libxl_ctx_alloc(&libxl_driver->ctx, LIBXL_VERSION, 0, NULL)) {
-        VIR_INFO("cannot initialize libxenlight context, probably not running in a Xen Dom0, disabling driver");
+    libxl_driver->logger =
+            (xentoollog_logger *)xtl_createlogger_stdiostream(libxl_driver->logger_file, XTL_DEBUG, 0);
+    if (!libxl_driver->logger) {
+        VIR_INFO("cannot create logger for libxenlight, disabling driver");
+        goto fail;
+    }
+
+    if (libxl_ctx_alloc(&libxl_driver->ctx,
+                       LIBXL_VERSION, 0,
+                       libxl_driver->logger)) {
+        VIR_INFO("cannot initialize libxenlight context, probably not running "
+                 "in a Xen Dom0, disabling driver");
         goto fail;
     }
 
@@ -1383,6 +1408,7 @@ libxlStateInitialize(bool privileged,
 error:
     ret = -1;
 fail:
+    VIR_FREE(log_file);
     if (libxl_driver)
         libxlDriverUnlock(libxl_driver);
     libxlStateCleanup();