Fixed trailer construction with limit on FreeBSD and macOS.

The ngx_chain_coalesce_file() function may produce more bytes to send then
requested in the limit passed, as it aligns the last file position
to send to memory page boundary.  As a result, (limit - send) may become
negative.  This resulted in big positive number when converted to size_t
while calling ngx_output_chain_to_iovec().

Another part of the problem is in ngx_chain_coalesce_file(): it changes cl
to the next chain link even if the current buffer is only partially sent
due to limit.

Therefore, if a file buffer was not expected to be fully sent due to limit,
and was followed by a memory buffer, nginx called sendfile() with a part
of the file buffer, and the memory buffer in trailer.  If there were enough
room in the socket buffer, this resulted in a part of the file buffer being
skipped, and corresponding part of the memory buffer sent instead.

The bug was introduced in 8e903522c17a (1.7.8).  Configurations affected
are ones using limits, that is, limit_rate and/or sendfile_max_chunk, and
memory buffers after file ones (may happen when using subrequests or
with proxying with disk buffering).

Fix is to explicitly check if (send < limit) before constructing trailer
with ngx_output_chain_to_iovec().  Additionally, ngx_chain_coalesce_file()
was modified to preserve unfinished file buffers in cl.

diff --git a/src/core/ngx_buf.c b/src/core/ngx_buf.c
index d30a0a4fcad679d05244811adb8813e6ff1ddefb..1862a0606ab531f79ad4cfc0ae37f732c9fb8526 100644 (file)
--- a/src/core/ngx_buf.c
+++ b/src/core/ngx_buf.c
@@ -246,6 +246,9 @@ ngx_chain_coalesce_file(ngx_chain_t **in, off_t limit)
             if (aligned <= cl->buf->file_last) {
                 size = aligned - cl->buf->file_pos;
             }
+
+            total += size;
+            break;
         }
 
         total += size;

diff --git a/src/os/unix/ngx_darwin_sendfile_chain.c b/src/os/unix/ngx_darwin_sendfile_chain.c
index c802e9f9a163dff8627651a55424db35e4255ed1..2a76c154dd2326d8ce46b43fa7eae584c3c0440b 100644 (file)
--- a/src/os/unix/ngx_darwin_sendfile_chain.c
+++ b/src/os/unix/ngx_darwin_sendfile_chain.c
@@ -98,7 +98,7 @@ ngx_darwin_sendfile_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
 
             send += file_size;
 
-            if (header.count == 0) {
+            if (header.count == 0 && send < limit) {
 
                 /*
                  * create the trailer iovec and coalesce the neighbouring bufs

diff --git a/src/os/unix/ngx_freebsd_sendfile_chain.c b/src/os/unix/ngx_freebsd_sendfile_chain.c
index d0299f54fa9c3893e4e910d84864a553a19862c6..4822e72bb82802a6a6979c3b5994f3d59c6f83f8 100644 (file)
--- a/src/os/unix/ngx_freebsd_sendfile_chain.c
+++ b/src/os/unix/ngx_freebsd_sendfile_chain.c
@@ -114,15 +114,23 @@ ngx_freebsd_sendfile_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
 
             send += file_size;
 
-            /* create the trailer iovec and coalesce the neighbouring bufs */
+            if (send < limit) {
 
-            cl = ngx_output_chain_to_iovec(&trailer, cl, limit - send, c->log);
+                /*
+                 * create the trailer iovec and coalesce the neighbouring bufs
+                 */
 
-            if (cl == NGX_CHAIN_ERROR) {
-                return NGX_CHAIN_ERROR;
-            }
+                cl = ngx_output_chain_to_iovec(&trailer, cl, limit - send,
+                                               c->log);
+                if (cl == NGX_CHAIN_ERROR) {
+                    return NGX_CHAIN_ERROR;
+                }
+
+                send += trailer.size;
 
-            send += trailer.size;
+            } else {
+                trailer.count = 0;
+            }
 
             if (ngx_freebsd_use_tcp_nopush
                 && c->tcp_nopush == NGX_TCP_NOPUSH_UNSET)