util: avoid symbol clash between json libraries

The jansson and json-glib libraries both export symbols with a json_
name prefix and json_object_iter_next() clashes between them.

Unfortunately json-glib is linked in by GTK, so any app using GTK and
libvirt will get a clash, resulting in SEGV. This also affects the NSS
module provided by libvirt

Instead of directly linking to jansson, use dlopen() with the RTLD_LOCAL
flag which allows us to hide the symbols from the application that loads
libvirt or the NSS module.

Some preprocessor black magic and wrapper functions are used to redirect
calls into the dlopen resolved symbols.
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

libvirt.spec.in

@@ -898,6 +898,8 @@ Requires: ncurses
 Requires: gettext
 # Needed by virt-pki-validate script.
 Requires: gnutls-utils
+# We dlopen(libjansson.so.4), so need an explicit dep
+Requires: jansson
 %if %{with_bash_completion}
 Requires: %{name}-bash-completion = %{version}-%{release}
 %endif

src/Makefile.am

@@ -552,7 +552,6 @@ libvirt_admin_la_CFLAGS += \
 
 libvirt_admin_la_LIBADD += \
 		$(CAPNG_LIBS) \
-		$(JANSSON_LIBS) \
 		$(DEVMAPPER_LIBS) \
 		$(LIBXML_LIBS) \
 		$(SSH2_LIBS) \
@@ -690,6 +689,7 @@ libvirt_setuid_rpc_client_la_SOURCES = \
 		util/virhashcode.c \
 		util/virhostcpu.c \
 		util/virjson.c \
+		util/virjsoncompat.c \
 		util/virlog.c \
 		util/virobject.c \
 		util/virpidfile.c \
@@ -961,6 +961,8 @@ libvirt_nss_la_SOURCES = \
 		util/virhashcode.h \
 		util/virjson.c \
 		util/virjson.h \
+		util/virjsoncompat.c \
+		util/virjsoncompat.h \
 		util/virkmod.c \
 		util/virkmod.h \
 		util/virlease.c \
@@ -999,10 +1001,6 @@ libvirt_nss_la_CFLAGS = \
 libvirt_nss_la_LDFLAGS = \
 		$(AM_LDFLAGS) \
 		$(NULL)
-
-libvirt_nss_la_LIBADD = \
-		$(JANSSON_LIBS) \
-		$(NULL)
 endif WITH_NSS
 
 

src/util/Makefile.inc.am

@@ -86,6 +86,8 @@ UTIL_SOURCES = \
 	util/viriscsi.h \
 	util/virjson.c \
 	util/virjson.h \
+	util/virjsoncompat.c \
+	util/virjsoncompat.h \
 	util/virkeycode.c \
 	util/virkeycode.h \
 	util/virkeyfile.c \
@@ -264,7 +266,6 @@ libvirt_util_la_CFLAGS = \
 	$(NULL)
 libvirt_util_la_LIBADD = \
 	$(CAPNG_LIBS) \
-	$(JANSSON_LIBS) \
 	$(LIBNL_LIBS) \
 	$(THREAD_LIBS) \
 	$(AUDIT_LIBS) \

src/util/virjson.c

@@ -1437,7 +1437,8 @@ virJSONValueCopy(const virJSONValue *in)
 
 
 #if WITH_JANSSON
-# include <jansson.h>
+
+# include "virjsoncompat.h"
 
 static virJSONValuePtr
 virJSONValueFromJansson(json_t *json)
@@ -1524,6 +1525,9 @@ virJSONValueFromString(const char *jsonstring)
     size_t flags = JSON_REJECT_DUPLICATES |
                    JSON_DECODE_ANY;
 
+    if (virJSONInitialize() < 0)
+        return NULL;
+
     if (!(json = json_loads(jsonstring, flags, &error))) {
         virReportError(VIR_ERR_INTERNAL_ERROR,
                        _("failed to parse JSON %d:%d: %s"),
@@ -1630,6 +1634,9 @@ virJSONValueToString(virJSONValuePtr object,
     json_t *json;
     char *str = NULL;
 
+    if (virJSONInitialize() < 0)
+        return NULL;
+
     if (pretty)
         flags |= JSON_INDENT(2);
     else

src/util/virjsoncompat.c

+/*
+ * virjsoncompat.c: JSON object parsing/formatting
+ *
+ * Copyright (C) 2018 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <config.h>
+
+#include "virthread.h"
+#include "virerror.h"
+#define VIR_JSON_COMPAT_IMPL
+#include "virjsoncompat.h"
+
+#define VIR_FROM_THIS VIR_FROM_NONE
+
+#if WITH_JANSSON
+
+# include <dlfcn.h>
+
+json_t *(*json_array_ptr)(void);
+int (*json_array_append_new_ptr)(json_t *array, json_t *value);
+json_t *(*json_array_get_ptr)(const json_t *array, size_t index);
+size_t (*json_array_size_ptr)(const json_t *array);
+void (*json_delete_ptr)(json_t *json);
+char *(*json_dumps_ptr)(const json_t *json, size_t flags);
+json_t *(*json_false_ptr)(void);
+json_t *(*json_integer_ptr)(json_int_t value);
+json_int_t (*json_integer_value_ptr)(const json_t *integer);
+json_t *(*json_loads_ptr)(const char *input, size_t flags, json_error_t *error);
+json_t *(*json_null_ptr)(void);
+json_t *(*json_object_ptr)(void);
+void *(*json_object_iter_ptr)(json_t *object);
+const char *(*json_object_iter_key_ptr)(void *iter);
+void *(*json_object_iter_next_ptr)(json_t *object, void *iter);
+json_t *(*json_object_iter_value_ptr)(void *iter);
+void *(*json_object_key_to_iter_ptr)(const char *key);
+int (*json_object_set_new_ptr)(json_t *object, const char *key, json_t *value);
+json_t *(*json_real_ptr)(double value);
+double (*json_real_value_ptr)(const json_t *real);
+json_t *(*json_string_ptr)(const char *value);
+const char *(*json_string_value_ptr)(const json_t *string);
+json_t *(*json_true_ptr)(void);
+
+
+static int
+virJSONJanssonOnceInit(void)
+{
+    void *handle = dlopen("libjansson.so.4", RTLD_LAZY|RTLD_LOCAL|RTLD_NODELETE);
+    if (!handle) {
+        virReportError(VIR_ERR_NO_SUPPORT,
+                       _("libjansson.so.4 JSON library not available: %s"), dlerror());
+        return -1;
+    }
+
+# define LOAD(name) \
+    do { \
+        if (!(name ## _ptr = dlsym(handle, #name))) { \
+            virReportError(VIR_ERR_NO_SUPPORT, \
+                           _("missing symbol '%s' in libjansson.so.4: %s"), #name, dlerror()); \
+            return -1; \
+        } \
+    } while (0)
+
+    LOAD(json_array);
+    LOAD(json_array_append_new);
+    LOAD(json_array_get);
+    LOAD(json_array_size);
+    LOAD(json_delete);
+    LOAD(json_dumps);
+    LOAD(json_false);
+    LOAD(json_integer);
+    LOAD(json_integer_value);
+    LOAD(json_loads);
+    LOAD(json_null);
+    LOAD(json_object);
+    LOAD(json_object_iter);
+    LOAD(json_object_iter_key);
+    LOAD(json_object_iter_next);
+    LOAD(json_object_iter_value);
+    LOAD(json_object_key_to_iter);
+    LOAD(json_object_set_new);
+    LOAD(json_real);
+    LOAD(json_real_value);
+    LOAD(json_string);
+    LOAD(json_string_value);
+    LOAD(json_true);
+
+    return 0;
+}
+
+VIR_ONCE_GLOBAL_INIT(virJSONJansson);
+
+int
+virJSONInitialize(void)
+{
+    return virJSONJanssonInitialize();
+}
+
+json_t *
+json_array_impl(void)
+{
+    return json_array_ptr();
+}
+
+
+int
+json_array_append_new_impl(json_t *array, json_t *value)
+{
+    return json_array_append_new_ptr(array, value);
+}
+
+
+json_t *
+json_array_get_impl(const json_t *array, size_t index)
+{
+    return json_array_get_ptr(array, index);
+}
+
+
+size_t
+json_array_size_impl(const json_t *array)
+{
+    return json_array_size_ptr(array);
+}
+
+
+void
+json_delete_impl(json_t *json)
+{
+    return json_delete_ptr(json);
+}
+
+
+char *
+json_dumps_impl(const json_t *json, size_t flags)
+{
+    return json_dumps_ptr(json, flags);
+}
+
+
+json_t *
+json_false_impl(void)
+{
+    return json_false_ptr();
+}
+
+
+json_t *
+json_integer_impl(json_int_t value)
+{
+    return json_integer_ptr(value);
+}
+
+
+json_int_t
+json_integer_value_impl(const json_t *integer)
+{
+    return json_integer_value_ptr(integer);
+}
+
+
+json_t *
+json_loads_impl(const char *input, size_t flags, json_error_t *error)
+{
+    return json_loads_ptr(input, flags, error);
+}
+
+
+json_t *
+json_null_impl(void)
+{
+    return json_null_ptr();
+}
+
+
+json_t *
+json_object_impl(void)
+{
+    return json_object_ptr();
+}
+
+
+void *
+json_object_iter_impl(json_t *object)
+{
+    return json_object_iter_ptr(object);
+}
+
+
+const char *
+json_object_iter_key_impl(void *iter)
+{
+    return json_object_iter_key_ptr(iter);
+}
+
+
+void *
+json_object_iter_next_impl(json_t *object, void *iter)
+{
+    return json_object_iter_next_ptr(object, iter);
+}
+
+
+json_t *
+json_object_iter_value_impl(void *iter)
+{
+    return json_object_iter_value_ptr(iter);
+}
+
+
+void *
+json_object_key_to_iter_impl(const char *key)
+{
+    return json_object_key_to_iter_ptr(key);
+}
+
+
+int
+json_object_set_new_impl(json_t *object, const char *key, json_t *value)
+{
+    return json_object_set_new_ptr(object, key, value);
+}
+
+
+json_t *
+json_real_impl(double value)
+{
+    return json_real_ptr(value);
+}
+
+
+double
+json_real_value_impl(const json_t *real)
+{
+    return json_real_value_ptr(real);
+}
+
+
+json_t *
+json_string_impl(const char *value)
+{
+    return json_string_ptr(value);
+}
+
+
+const char *
+json_string_value_impl(const json_t *string)
+{
+    return json_string_value_ptr(string);
+}
+
+
+json_t *
+json_true_impl(void)
+{
+    return json_true_ptr();
+}
+
+#endif /* WITH_JANSSON */

src/util/virjsoncompat.h

+/*
+ * virjsoncompat.h: JSON object parsing/formatting
+ *
+ * Copyright (C) 2018 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ */
+
+
+#ifndef __VIR_JSON_COMPAT_H_
+# define __VIR_JSON_COMPAT_H_
+
+# if WITH_JANSSON
+#  ifndef VIR_JSON_COMPAT_IMPL
+
+#   define json_array json_array_impl
+#   define json_array_append_new json_array_append_new_impl
+#   define json_array_get json_array_get_impl
+#   define json_array_size json_array_size_impl
+#   define json_delete json_delete_impl
+#   define json_dumps json_dumps_impl
+#   define json_false json_false_impl
+#   define json_integer json_integer_impl
+#   define json_integer_value json_integer_value_impl
+#   define json_loads json_loads_impl
+#   define json_null json_null_impl
+#   define json_object json_object_impl
+#   define json_object_iter json_object_iter_impl
+#   define json_object_iter_key json_object_iter_key_impl
+#   define json_object_iter_next json_object_iter_next_impl
+#   define json_object_iter_value json_object_iter_value_impl
+#   define json_object_key_to_iter json_object_key_to_iter_impl
+#   define json_object_set_new json_object_set_new_impl
+#   define json_real json_real_impl
+#   define json_real_value json_real_value_impl
+#   define json_string json_string_impl
+#   define json_string_value json_string_value_impl
+#   define json_true json_true_impl
+
+#  endif /* ! VIR_JSON_COMPAT_IMPL */
+
+#  include <jansson.h>
+
+#  ifdef VIR_JSON_COMPAT_IMPL
+
+json_t *json_array_impl(void);
+int json_array_append_new_impl(json_t *array, json_t *value);
+json_t *json_array_get_impl(const json_t *array, size_t index);
+size_t json_array_size_impl(const json_t *array);
+void json_delete_impl(json_t *json);
+char *json_dumps_impl(const json_t *json, size_t flags);
+json_t *json_false_impl(void);
+json_t *json_integer_impl(json_int_t value);
+json_int_t json_integer_value_impl(const json_t *integer);
+json_t *json_loads_impl(const char *input, size_t flags, json_error_t *error);
+json_t *json_null_impl(void);
+json_t *json_object_impl(void);
+void *json_object_iter_impl(json_t *object);
+const char *json_object_iter_key_impl(void *iter);
+void *json_object_iter_next_impl(json_t *object, void *iter);
+json_t *json_object_iter_value_impl(void *iter);
+void *json_object_key_to_iter_impl(const char *key);
+int json_object_set_new_impl(json_t *object, const char *key, json_t *value);
+json_t *json_real_impl(double value);
+double json_real_value_impl(const json_t *real);
+json_t *json_string_impl(const char *value);
+const char *json_string_value_impl(const json_t *string);
+json_t *json_true_impl(void);
+
+#  endif /* VIR_JSON_COMPAT_IMPL */
+# endif /* WITH_JANSSON */
+
+int virJSONInitialize(void);
+
+#endif /* __VIR_JSON_COMPAT_H_ */