bugfix: using error codes (ngx.ERROR or >=300) in ngx.exit() in header_filter_by_lua* might lead to Lua stack overflow.

Author: agentzh

src/ngx_http_lua_headerfilterby.c

@@ -131,6 +131,11 @@ ngx_http_lua_header_filter_by_chunk(lua_State *L, ngx_http_request_t *r)
     dd("exited: %d, exit code: %d, old exit code: %d",
        (int) ctx->exited, (int) ctx->exit_code, (int) old_exit_code);
 
+#if 1
+    /*  clear Lua stack */
+    lua_settop(L, 0);
+#endif
+
     if (ctx->exited && ctx->exit_code != old_exit_code) {
         if (ctx->exit_code == NGX_ERROR) {
             return NGX_ERROR;
@@ -147,9 +152,6 @@ ngx_http_lua_header_filter_by_chunk(lua_State *L, ngx_http_request_t *r)
         return NGX_DECLINED;
     }
 
-    /*  clear Lua stack */
-    lua_settop(L, 0);
-
     return NGX_OK;
 }
 

t/041-header-filter.t

@@ -767,3 +767,28 @@ GET /lua?a=1&b=2
 --- error_log eval
 qr/failed to load external Lua file ".*?test2\.lua": cannot open .*? No such file or directory/
 
+
+
+=== TEST 41: filter finalize
+--- config
+    error_page 582 = /bar;
+    location = /t {
+        echo ok;
+        header_filter_by_lua '
+            return ngx.exit(582)
+        ';
+    }
+
+    location = /bar {
+        echo hi;
+        header_filter_by_lua '
+            return ngx.exit(302)
+        ';
+    }
+--- request
+GET /t
+--- response_body_like: 302 Found
+--- error_code: 302
+--- no_error_log
+[error]
+