Fixed null pointer dereference with $upstream_cache_last_modified.

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index 9570ccc7eeff8ea4cd69b7b6b66d4d79a0be3170..c148f38d06727274a0aedbfb29bddfa805c156a5 100644 (file)
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -4555,7 +4555,8 @@ ngx_http_upstream_cache_last_modified(ngx_http_request_t *r,
 {
     u_char  *p;
 
-    if (!r->upstream->conf->cache_revalidate
+    if (r->upstream == NULL
+        || !r->upstream->conf->cache_revalidate
         || r->upstream->cache_status != NGX_HTTP_CACHE_EXPIRED
         || r->cache->last_modified == -1)
     {