Lighttpd

Sending two consecutive request where the first request is for a CGI and the second is for a static file seem to trigger a race condition causing the CGI to be unhandled. No response is generated for the CGI request, the static file however is served.

The issue was observed when posting a large file to the CGI, then almost simultaneously fetching a spinner gif image.

Disabling cache in the browser (thus forcing update of the spinner graphic) makes this issue very reproducible.

If I'm not mistaken it seems to have something to do with the second request (static file) calling URIHANDLER_FUNC(cgi_is_handled) of mod_cgi replacing the current plugin data before the actual fork and exec of the cgi request takes place.

When the error happens I've observed that, in the function SUBREQUEST_FUNC(mod_cgi_handle_subrequest), the following handler is NULL.

mod_cgi.c, line 1445, if (!handler) return HANDLER_GO_ON; /*(should not happen; checked in cgi_is_handled())*/

A closer look at the array p->conf.cgi, passed to the cgi_get_handler the line before, showed that it was of zero length. Normally this array contains the entry ".cgi".

I'm on the master branch commit f635ae7a07f56db636ab557a5f24bbcaf0b1bcd9 on GitHub.

Attached is a lighttpd log file of the event (as much detail I could enable).