commit bfcae97ed5929d790838007bd7ea4756b0f3ce2d
author Roman Arutyunyan <arut@nginx.com> Thu Mar 01 18:38:39 2018 +0300
committer Roman Arutyunyan <arut@nginx.com> Thu Mar 01 18:38:39 2018 +0300
tree 89fb6e3628742f5500713fd1d6141034493ae366
parent e398ac593cc47b475d545cabc34500112327b129

Postpone filter: prevented uninitialized r->out.

The r->out chain link could be left uninitialized in case of error.
A segfault could happen if the subrequest handler accessed it.
The issue was introduced in commit 20f139e9ffa8.

src/http/ngx_http_postpone_filter_module.c

diff --git a/src/http/ngx_http_postpone_filter_module.c b/src/http/ngx_http_postpone_filter_module.c
index ded70b3..599d263 100644
--- a/src/http/ngx_http_postpone_filter_module.c
+++ b/src/http/ngx_http_postpone_filter_module.c
@@ -191,11 +191,6 @@
                    "http postpone filter in memory");
 
     if (r->out == NULL) {
-        r->out = ngx_alloc_chain_link(r->pool);
-        if (r->out == NULL) {
-            return NGX_ERROR;
-        }
-
         clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
 
         if (r->headers_out.content_length_n != -1) {
@@ -218,6 +213,11 @@
 
         b->last_buf = 1;
 
+        r->out = ngx_alloc_chain_link(r->pool);
+        if (r->out == NULL) {
+            return NGX_ERROR;
+        }
+
         r->out->buf = b;
         r->out->next = NULL;
     }