Lua Variable access bug?

[agentzh]

On Wed, May 16, 2012 at 10:16 AM, Sirsiwal, Umesh <usirsiwal at verivue.com> wrote:
>
> I think issue exists because of the way ngx_http_variables_init_vars is
> written. It changes the flags in the static ngx_http_core_variables variable.
> During the first configuration read cycle where $http_host is indexed, the
> flag changes to indexed. During the second configuration read cycle where
> the the $http_host variable should not be indexed, the flags still remain
> INDEXED. That confuses ngx_http_get_variable later.
>

This is indeed an issue in the nginx core and it should affect other
modules other than ngx_lua.

I think the ngx_http_variables_add_core_vars function should pass a
copy of the ngx_http_variable_t entries in the static variable
ngx_http_core_variables.

Could you please try the patch below for nginx 1.0.15? I've confirmed
that it can also be applied cleanly to nginx 1.2.0.

Thanks!
-agentzh

--- nginx-1.0.15/src/http/ngx_http_variables.c	2012-03-05
20:36:51.000000000 +0800
+++ nginx-1.0.15-patched/src/http/ngx_http_variables.c	2012-05-17
16:21:42.120968722 +0800
@@ -1898,6 +1898,7 @@
 {
     ngx_int_t                   rc;
     ngx_http_variable_t        *v;
+    ngx_http_variable_t        *value;
     ngx_http_core_main_conf_t  *cmcf;

     cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module);
@@ -1918,7 +1919,14 @@
     }

     for (v = ngx_http_core_variables; v->name.len; v++) {
-        rc = ngx_hash_add_key(cmcf->variables_keys, &v->name, v,
+        value = ngx_palloc(cf->pool, sizeof(ngx_http_variable_t));
+        if (value == NULL) {
+            return NGX_ERROR;
+        }
+
+        *value = *v;
+
+        rc = ngx_hash_add_key(cmcf->variables_keys, &value->name, value,
                               NGX_HASH_READONLY_KEY);

         if (rc == NGX_OK) {
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