config-parser: no longer get past the last NULL passed to locate_attributes

Fixes: bc86794f23fa53
Fixes:
```
==302818==ERROR: AddressSanitizer: stack-buffer-underflow on address 0x7ffd6ac253c0 at pc 0x000000534d0b bp 0x7ffd6ac24e10 sp 0x7ffd6ac24e08
READ of size 8 at 0x7ffd6ac253c0 thread T0
    #0 0x534d0a in locate_attributes /home/vagrant/dbus/build/../bus/config-parser.c:658:16
    #1 0x52ea3f in start_busconfig_child /home/vagrant/dbus/build/../bus/config-parser.c:1080:12
    #2 0x52cca4 in bus_config_parser_start_element /home/vagrant/dbus/build/../bus/config-parser.c:2039:14
    #3 0x52b82b in expat_StartElementHandler /home/vagrant/dbus/build/../bus/config-loader-expat.c:107:8
    #4 0x7f2179f2d2bd  (/lib64/libexpat.so.1+0xd2bd) (BuildId: 0165eed77c910f6ef2227d21afa9c5c5ed5849c2)
    #5 0x7f2179f2aed3  (/lib64/libexpat.so.1+0xaed3) (BuildId: 0165eed77c910f6ef2227d21afa9c5c5ed5849c2)
    #6 0x7f2179f2c9ec  (/lib64/libexpat.so.1+0xc9ec) (BuildId: 0165eed77c910f6ef2227d21afa9c5c5ed5849c2)
    #7 0x7f2179f30a8e in XML_ParseBuffer (/lib64/libexpat.so.1+0x10a8e) (BuildId: 0165eed77c910f6ef2227d21afa9c5c5ed5849c2)
    #8 0x52b040 in bus_config_load /home/vagrant/dbus/build/../bus/config-loader-expat.c:259:9
    #9 0x523c8a in bus_context_new /home/vagrant/dbus/build/../bus/bus.c:828:12
    #10 0x521056 in main /home/vagrant/dbus/build/../bus/main.c:716:13
    #11 0x7f2179a2954f in __libc_start_call_main (/lib64/libc.so.6+0x2954f) (BuildId: 9c5863396a11aab52ae8918ae01a362cefa855fe)
    #12 0x7f2179a29608 in __libc_start_main@GLIBC_2.2.5 (/lib64/libc.so.6+0x29608) (BuildId: 9c5863396a11aab52ae8918ae01a362cefa855fe)
    #13 0x42a914 in _start (/home/vagrant/dbus/build/bus/dbus-daemon+0x42a914) (BuildId: df5369f85137975aff9bd398ae859706cc3c52ff)

Address 0x7ffd6ac253c0 is located in stack of thread T0 at offset 0 in frame
    #0 0x52cfaf in start_busconfig_child /home/vagrant/dbus/build/../bus/config-parser.c:733
```

Signed-off-by: Evgeny Vereshchagin <evvers@ya.ru>
(cherry picked from commit ae03bcdb1116a953d4d33661cf878e68cdfbb9fd)

diff --git a/bus/config-parser.c b/bus/config-parser.c
index f9b704772197c00a60ac6ee7e3fda1424f25e6d1..9f2e3c794784ef67b41d868dda5f7dfcc546a9f6 100644 (file)
--- a/bus/config-parser.c
+++ b/bus/config-parser.c
@@ -642,10 +642,11 @@ locate_attributes (BusConfigParser  *parser,
   va_start (args, first_attribute_retloc);
 
   name = va_arg (args, const char*);
-  retloc = va_arg (args, const char**);
+  retloc = NULL;
 
   while (name != NULL)
     {
+      retloc = va_arg (args, const char**);
       _dbus_assert (retloc != NULL);
       _dbus_assert (n_attrs < MAX_ATTRS);
 
@@ -655,7 +656,6 @@ locate_attributes (BusConfigParser  *parser,
       *retloc = NULL;
 
       name = va_arg (args, const char*);
-      retloc = va_arg (args, const char**);
     }
 
   va_end (args);