Negative size buffers detection.

In the past, there were several security issues which resulted in
worker process memory disclosure due to buffers with negative size.
It looks reasonable to check for such buffers in various places,
much like we already check for zero size buffers.

While here, removed "#if 1 / #endif" around zero size buffer checks.
It looks highly unlikely that we'll disable these checks anytime soon.

3 files changed, 132 insertions, 12 deletions

diff --git a/src/core/ngx_output_chain.c b/src/core/ngx_output_chain.c
index 7f5dc787e..5c3dbe872 100644
--- a/src/core/ngx_output_chain.c
+++ b/src/core/ngx_output_chain.c
@@ -126,6 +126,26 @@ ngx_output_chain(ngx_output_chain_ctx_t *ctx, ngx_chain_t *in)
                 continue;
             }
 
+            if (bsize < 0) {
+
+                ngx_log_error(NGX_LOG_ALERT, ctx->pool->log, 0,
+                              "negative size buf in output "
+                              "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+                              ctx->in->buf->temporary,
+                              ctx->in->buf->recycled,
+                              ctx->in->buf->in_file,
+                              ctx->in->buf->start,
+                              ctx->in->buf->pos,
+                              ctx->in->buf->last,
+                              ctx->in->buf->file,
+                              ctx->in->buf->file_pos,
+                              ctx->in->buf->file_last);
+
+                ngx_debug_point();
+
+                return NGX_ERROR;
+            }
+
             if (ngx_output_chain_as_is(ctx, ctx->in->buf)) {
 
                 /* move the chain link to the output chain */
@@ -665,7 +685,6 @@ ngx_chain_writer(void *data, ngx_chain_t *in)
 
     for (size = 0; in; in = in->next) {
 
-#if 1
         if (ngx_buf_size(in->buf) == 0 && !ngx_buf_special(in->buf)) {
 
             ngx_log_error(NGX_LOG_ALERT, ctx->pool->log, 0,
@@ -685,7 +704,26 @@ ngx_chain_writer(void *data, ngx_chain_t *in)
 
             continue;
         }
-#endif
+
+        if (ngx_buf_size(in->buf) < 0) {
+
+            ngx_log_error(NGX_LOG_ALERT, ctx->pool->log, 0,
+                          "negative size buf in chain writer "
+                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+                          in->buf->temporary,
+                          in->buf->recycled,
+                          in->buf->in_file,
+                          in->buf->start,
+                          in->buf->pos,
+                          in->buf->last,
+                          in->buf->file,
+                          in->buf->file_pos,
+                          in->buf->file_last);
+
+            ngx_debug_point();
+
+            return NGX_ERROR;
+        }
 
         size += ngx_buf_size(in->buf);
 
@@ -709,7 +747,6 @@ ngx_chain_writer(void *data, ngx_chain_t *in)
 
     for (cl = ctx->out; cl; cl = cl->next) {
 
-#if 1
         if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
 
             ngx_log_error(NGX_LOG_ALERT, ctx->pool->log, 0,
@@ -729,7 +766,26 @@ ngx_chain_writer(void *data, ngx_chain_t *in)
 
             continue;
         }
-#endif
+
+        if (ngx_buf_size(cl->buf) < 0) {
+
+            ngx_log_error(NGX_LOG_ALERT, ctx->pool->log, 0,
+                          "negative size buf in chain writer "
+                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+                          cl->buf->temporary,
+                          cl->buf->recycled,
+                          cl->buf->in_file,
+                          cl->buf->start,
+                          cl->buf->pos,
+                          cl->buf->last,
+                          cl->buf->file,
+                          cl->buf->file_pos,
+                          cl->buf->file_last);
+
+            ngx_debug_point();
+
+            return NGX_ERROR;
+        }
 
         size += ngx_buf_size(cl->buf);
     }
diff --git a/src/http/ngx_http_write_filter_module.c b/src/http/ngx_http_write_filter_module.c
index 003623151..3f18d76f2 100644
--- a/src/http/ngx_http_write_filter_module.c
+++ b/src/http/ngx_http_write_filter_module.c
@@ -80,7 +80,6 @@ ngx_http_write_filter(ngx_http_request_t *r, ngx_chain_t *in)
                        cl->buf->file_pos,
                        cl->buf->file_last - cl->buf->file_pos);
 
-#if 1
         if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
             ngx_log_error(NGX_LOG_ALERT, c->log, 0,
                           "zero size buf in writer "
@@ -98,7 +97,24 @@ ngx_http_write_filter(ngx_http_request_t *r, ngx_chain_t *in)
             ngx_debug_point();
             return NGX_ERROR;
         }
-#endif
+
+        if (ngx_buf_size(cl->buf) < 0) {
+            ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+                          "negative size buf in writer "
+                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+                          cl->buf->temporary,
+                          cl->buf->recycled,
+                          cl->buf->in_file,
+                          cl->buf->start,
+                          cl->buf->pos,
+                          cl->buf->last,
+                          cl->buf->file,
+                          cl->buf->file_pos,
+                          cl->buf->file_last);
+
+            ngx_debug_point();
+            return NGX_ERROR;
+        }
 
         size += ngx_buf_size(cl->buf);
 
@@ -136,7 +152,6 @@ ngx_http_write_filter(ngx_http_request_t *r, ngx_chain_t *in)
                        cl->buf->file_pos,
                        cl->buf->file_last - cl->buf->file_pos);
 
-#if 1
         if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
             ngx_log_error(NGX_LOG_ALERT, c->log, 0,
                           "zero size buf in writer "
@@ -154,7 +169,24 @@ ngx_http_write_filter(ngx_http_request_t *r, ngx_chain_t *in)
             ngx_debug_point();
             return NGX_ERROR;
         }
-#endif
+
+        if (ngx_buf_size(cl->buf) < 0) {
+            ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+                          "negative size buf in writer "
+                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+                          cl->buf->temporary,
+                          cl->buf->recycled,
+                          cl->buf->in_file,
+                          cl->buf->start,
+                          cl->buf->pos,
+                          cl->buf->last,
+                          cl->buf->file,
+                          cl->buf->file_pos,
+                          cl->buf->file_last);
+
+            ngx_debug_point();
+            return NGX_ERROR;
+        }
 
         size += ngx_buf_size(cl->buf);
 
diff --git a/src/stream/ngx_stream_write_filter_module.c b/src/stream/ngx_stream_write_filter_module.c
index 8fdcd372b..24326c60e 100644
--- a/src/stream/ngx_stream_write_filter_module.c
+++ b/src/stream/ngx_stream_write_filter_module.c
@@ -104,7 +104,6 @@ ngx_stream_write_filter(ngx_stream_session_t *s, ngx_chain_t *in,
                        cl->buf->file_pos,
                        cl->buf->file_last - cl->buf->file_pos);
 
-#if 1
         if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
             ngx_log_error(NGX_LOG_ALERT, c->log, 0,
                           "zero size buf in writer "
@@ -122,7 +121,24 @@ ngx_stream_write_filter(ngx_stream_session_t *s, ngx_chain_t *in,
             ngx_debug_point();
             return NGX_ERROR;
         }
-#endif
+
+        if (ngx_buf_size(cl->buf) < 0) {
+            ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+                          "negative size buf in writer "
+                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+                          cl->buf->temporary,
+                          cl->buf->recycled,
+                          cl->buf->in_file,
+                          cl->buf->start,
+                          cl->buf->pos,
+                          cl->buf->last,
+                          cl->buf->file,
+                          cl->buf->file_pos,
+                          cl->buf->file_last);
+
+            ngx_debug_point();
+            return NGX_ERROR;
+        }
 
         size += ngx_buf_size(cl->buf);
 
@@ -160,7 +176,6 @@ ngx_stream_write_filter(ngx_stream_session_t *s, ngx_chain_t *in,
                        cl->buf->file_pos,
                        cl->buf->file_last - cl->buf->file_pos);
 
-#if 1
         if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
             ngx_log_error(NGX_LOG_ALERT, c->log, 0,
                           "zero size buf in writer "
@@ -178,7 +193,24 @@ ngx_stream_write_filter(ngx_stream_session_t *s, ngx_chain_t *in,
             ngx_debug_point();
             return NGX_ERROR;
         }
-#endif
+
+        if (ngx_buf_size(cl->buf) < 0) {
+            ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+                          "negative size buf in writer "
+                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
+                          cl->buf->temporary,
+                          cl->buf->recycled,
+                          cl->buf->in_file,
+                          cl->buf->start,
+                          cl->buf->pos,
+                          cl->buf->last,
+                          cl->buf->file,
+                          cl->buf->file_pos,
+                          cl->buf->file_last);
+
+            ngx_debug_point();
+            return NGX_ERROR;
+        }
 
         size += ngx_buf_size(cl->buf);