9pfs: fix name_to_path assertion in v9fs_complete_rename()

The third parameter of v9fs_co_name_to_path() must not contain `/'
character.

The issue is most likely related to 9p2000.u protocol only.
Signed-off-by: NJan Dakinevich <jan.dakinevich@gmail.com>
[groug, regression caused by commit f57f5878 # 2.10]
Signed-off-by: NGreg Kurz <groug@kaod.org>

hw/9pfs/9p.c

@@ -2553,13 +2553,11 @@ static int coroutine_fn v9fs_complete_rename(V9fsPDU *pdu, V9fsFidState *fidp,
                                              int32_t newdirfid,
                                              V9fsString *name)
 {
-    char *end;
     int err = 0;
     V9fsPath new_path;
     V9fsFidState *tfidp;
     V9fsState *s = pdu->s;
     V9fsFidState *dirfidp = NULL;
-    char *old_name, *new_name;
 
     v9fs_path_init(&new_path);
     if (newdirfid != -1) {
@@ -2577,18 +2575,15 @@ static int coroutine_fn v9fs_complete_rename(V9fsPDU *pdu, V9fsFidState *fidp,
             goto out;
         }
     } else {
-        old_name = fidp->path.data;
-        end = strrchr(old_name, '/');
-        if (end) {
-            end++;
-        } else {
-            end = old_name;
-        }
-        new_name = g_malloc0(end - old_name + name->size + 1);
-        strncat(new_name, old_name, end - old_name);
-        strncat(new_name + (end - old_name), name->data, name->size);
-        err = v9fs_co_name_to_path(pdu, NULL, new_name, &new_path);
-        g_free(new_name);
+        char *dir_name = g_path_get_dirname(fidp->path.data);
+        V9fsPath dir_path;
+
+        v9fs_path_init(&dir_path);
+        v9fs_path_sprintf(&dir_path, "%s", dir_name);
+        g_free(dir_name);
+
+        err = v9fs_co_name_to_path(pdu, &dir_path, name->data, &new_path);
+        v9fs_path_free(&dir_path);
         if (err < 0) {
             goto out;
         }