Image filter: large image handling.

If Content-Length header is not set, and the image size is larger than the
buffer size, client will hang until a timeout occurs.

Now NGX_HTTP_UNSUPPORTED_MEDIA_TYPE is returned immediately.

diff -r d1403de41631 -r 4fae04f332b4
src/http/modules/ngx_http_image_filter_module.c

src/http/modules/ngx_http_image_filter_module.c

diff --git a/src/http/modules/ngx_http_image_filter_module.c b/src/http/modules/ngx_http_image_filter_module.c
index 6d3f47d..cc41ef0 100644
--- a/src/http/modules/ngx_http_image_filter_module.c
+++ b/src/http/modules/ngx_http_image_filter_module.c
@@ -478,7 +478,12 @@
                        "image buf: %uz", size);
 
         rest = ctx->image + ctx->length - p;
-        size = (rest < size) ? rest : size;
+
+        if (size > rest) {
+            ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                          "image filter: too big response");
+            return NGX_ERROR;
+        }
 
         p = ngx_cpymem(p, b->pos, size);
         b->pos += size;