xl: Fix adding additional config cmdline parameters

When checking the size of the buffer we hold for additional
config parameters passed on the command line we should take the
size of the to-be-added string into account. While at it, rework
the implementation to be cleaner and safer.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index 6e2fce786dae4a61ebe26260f1e0271bce1218c7..547b2f6fa5d445ba4b93ee24cbe71474e3d29591 100644 (file)
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -3179,21 +3179,17 @@ int main_create(int argc, char **argv)
         }
     }
 
-    memset(extra_config, 0, sizeof(extra_config));
-    while (optind < argc) {
-        if ((p = strchr(argv[optind], '='))) {
-            if (strlen(extra_config) + 1 < sizeof(extra_config)) {
-                if (strlen(extra_config))
-                    strcat(extra_config, "\n");
-                strcat(extra_config, argv[optind]);
-            }
+    extra_config[0] = '\0';
+    for (p = extra_config; optind < argc; optind++) {
+        if (strchr(argv[optind], '=') != NULL) {
+            p += snprintf(p, sizeof(extra_config) - (p - extra_config),
+                "%s\n", argv[optind]);
         } else if (!filename) {
             filename = argv[optind];
         } else {
             help("create");
             return 2;
         }
-        optind++;
     }
 
     memset(&dom_info, 0, sizeof(dom_info));