[nginx] FastCGI: fixed zero size buf alerts on extra data (ticket #2018).

[Maxim Dounin]

details:   https://hg.nginx.org/nginx/rev/da8d758aabeb
branches:  
changeset: 7689:da8d758aabeb
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Mon Jul 27 16:02:15 2020 +0300
description:
FastCGI: fixed zero size buf alerts on extra data (ticket #2018).

After 05e42236e95b (1.19.1) responses with extra data might result in
zero size buffers being generated and "zero size buf" alerts in writer
(if f->rest happened to be 0 when processing additional stdout data).

diffstat:

 src/http/modules/ngx_http_fastcgi_module.c |  28 ++++++++++++++++++++++------
 1 files changed, 22 insertions(+), 6 deletions(-)

diffs (59 lines):

diff -r 2f9214713666 -r da8d758aabeb src/http/modules/ngx_http_fastcgi_module.c
--- a/src/http/modules/ngx_http_fastcgi_module.c	Mon Jul 27 13:21:51 2020 +0300
+++ b/src/http/modules/ngx_http_fastcgi_module.c	Mon Jul 27 16:02:15 2020 +0300
@@ -2306,6 +2306,18 @@ ngx_http_fastcgi_input_filter(ngx_event_
             break;
         }
 
+        if (f->rest == -2) {
+            f->rest = r->upstream->headers_in.content_length_n;
+        }
+
+        if (f->rest == 0) {
+            ngx_log_error(NGX_LOG_WARN, p->log, 0,
+                          "upstream sent more data than specified in "
+                          "\"Content-Length\" header");
+            p->upstream_done = 1;
+            break;
+        }
+
         cl = ngx_chain_get_free_buf(p->pool, &p->free);
         if (cl == NULL) {
             return NGX_ERROR;
@@ -2349,11 +2361,7 @@ ngx_http_fastcgi_input_filter(ngx_event_
             b->last = f->last;
         }
 
-        if (f->rest == -2) {
-            f->rest = r->upstream->headers_in.content_length_n;
-        }
-
-        if (f->rest >= 0) {
+        if (f->rest > 0) {
 
             if (b->last - b->pos > f->rest) {
                 ngx_log_error(NGX_LOG_WARN, p->log, 0,
@@ -2564,6 +2572,14 @@ ngx_http_fastcgi_non_buffered_filter(voi
             break;
         }
 
+        if (f->rest == 0) {
+            ngx_log_error(NGX_LOG_WARN, r->connection->log, 0,
+                          "upstream sent more data than specified in "
+                          "\"Content-Length\" header");
+            u->length = 0;
+            break;
+        }
+
         cl = ngx_chain_get_free_buf(r->pool, &u->free_bufs);
         if (cl == NULL) {
             return NGX_ERROR;
@@ -2594,7 +2610,7 @@ ngx_http_fastcgi_non_buffered_filter(voi
             b->last = f->last;
         }
 
-        if (f->rest >= 0) {
+        if (f->rest > 0) {
 
             if (b->last - b->pos > f->rest) {
                 ngx_log_error(NGX_LOG_WARN, r->connection->log, 0,