[PATCH 27 of 31] Core: protect from subrequest loops

[Maxim Dounin]

# HG changeset patch
# User Maxim Dounin <mdounin at mdounin.ru>
# Date 1309187571 -14400
# Node ID 283a416b2235d5383c12a975edc8866f007fb628
# Parent  f5fc40783ddcbf4db33859ee2a9bce54cf32c350
Core: protect from subrequest loops.

Without protection subrequest loop results in r->count overflow and
SIGSEGV.  Protection was broken in 0.7.25.

Note that this also limits number of parallel subrequests.  This
wasn't exactly the case before 0.7.25 as local subrequests were
completed directly.

See here for details:

http://nginx.org/pipermail/nginx-ru/2010-February/032184.html

diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -2287,7 +2287,6 @@ ngx_http_subrequest(ngx_http_request_t *
     sr->start_sec = tp->sec;
     sr->start_msec = tp->msec;
 
-    r->main->subrequests++;
     r->main->count++;
 
     *psr = sr;
diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -1981,6 +1981,7 @@ ngx_http_finalize_request(ngx_http_reque
         if (r == c->data) {
 
             r->main->count--;
+            r->main->subrequests++;
 
             if (!r->logged) {