[nginx] HTTP/2: limited number of DATA frames.

[Maxim Dounin]

details:   https://hg.nginx.org/nginx/rev/99b6733876c4
branches:  stable-1.16
changeset: 7555:99b6733876c4
user:      Ruslan Ermilov <ru at nginx.com>
date:      Tue Aug 13 15:43:36 2019 +0300
description:
HTTP/2: limited number of DATA frames.

Fixed excessive memory growth and CPU usage if stream windows are
manipulated in a way that results in generating many small DATA frames.
Fix is to limit the number of simultaneously allocated DATA frames.

diffstat:

 src/http/v2/ngx_http_v2.c               |   2 ++
 src/http/v2/ngx_http_v2.h               |   2 ++
 src/http/v2/ngx_http_v2_filter_module.c |  22 +++++++++++++++++-----
 3 files changed, 21 insertions(+), 5 deletions(-)

diffs (67 lines):

diff --git a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c
--- a/src/http/v2/ngx_http_v2.c
+++ b/src/http/v2/ngx_http_v2.c
@@ -4369,6 +4369,8 @@ ngx_http_v2_close_stream(ngx_http_v2_str
      */
     pool = stream->pool;
 
+    h2c->frames -= stream->frames;
+
     ngx_http_free_request(stream->request, rc);
 
     if (pool != h2c->state.pool) {
diff --git a/src/http/v2/ngx_http_v2.h b/src/http/v2/ngx_http_v2.h
--- a/src/http/v2/ngx_http_v2.h
+++ b/src/http/v2/ngx_http_v2.h
@@ -192,6 +192,8 @@ struct ngx_http_v2_stream_s {
 
     ngx_buf_t                       *preread;
 
+    ngx_uint_t                       frames;
+
     ngx_http_v2_out_frame_t         *free_frames;
     ngx_chain_t                     *free_frame_headers;
     ngx_chain_t                     *free_bufs;
diff --git a/src/http/v2/ngx_http_v2_filter_module.c b/src/http/v2/ngx_http_v2_filter_module.c
--- a/src/http/v2/ngx_http_v2_filter_module.c
+++ b/src/http/v2/ngx_http_v2_filter_module.c
@@ -1663,22 +1663,34 @@ static ngx_http_v2_out_frame_t *
 ngx_http_v2_filter_get_data_frame(ngx_http_v2_stream_t *stream,
     size_t len, ngx_chain_t *first, ngx_chain_t *last)
 {
-    u_char                    flags;
-    ngx_buf_t                *buf;
-    ngx_chain_t              *cl;
-    ngx_http_v2_out_frame_t  *frame;
+    u_char                     flags;
+    ngx_buf_t                 *buf;
+    ngx_chain_t               *cl;
+    ngx_http_v2_out_frame_t   *frame;
+    ngx_http_v2_connection_t  *h2c;
 
     frame = stream->free_frames;
+    h2c = stream->connection;
 
     if (frame) {
         stream->free_frames = frame->next;
 
-    } else {
+    } else if (h2c->frames < 10000) {
         frame = ngx_palloc(stream->request->pool,
                            sizeof(ngx_http_v2_out_frame_t));
         if (frame == NULL) {
             return NULL;
         }
+
+        stream->frames++;
+        h2c->frames++;
+
+    } else {
+        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
+                      "http2 flood detected");
+
+        h2c->connection->error = 1;
+        return NULL;
     }
 
     flags = last->buf->last_buf ? NGX_HTTP_V2_END_STREAM_FLAG : 0;