nginx 0.7.55 *) Bugfix: the http_XXX parameters in "proxy_cache_use_stale" and "fastcgi_cache_use_stale" directives did not work. *) Bugfix: fastcgi cache did not cache header only responses. *) Bugfix: of "select() failed (9: Bad file descriptor)" error in nginx/Unix and "select() failed (10022: ...)" error in nginx/Windows. *) Bugfix: a segmentation fault might occur in worker process, if an "debug_connection" directive was used; the bug had appeared in 0.7.54. *) Bugfix: fix ngx_http_image_filter_module building errors. *) Bugfix: the files bigger than 2G could not be transferred using $r->sendfile. Thanks to Maxim Dounin.

--- a/src/event/ngx_event_pipe.c
+++ b/src/event/ngx_event_pipe.c
@@ -397,7 +397,7 @@ ngx_event_pipe_read_upstream(ngx_event_p
 
         p->free_raw_bufs = p->free_raw_bufs->next;
 
-        if (p->free_bufs) {
+        if (p->free_bufs && p->buf_to_file == NULL) {
             for (cl = p->free_raw_bufs; cl; cl = cl->next) {
                 if (cl->buf->shadow == NULL) {
                     ngx_pfree(p->pool, cl->buf->start);