Resolver: protection from duplicate responses.
If we already had CNAME in resolver node (i.e. rn->cnlen and rn->u.cname
set), and got additional response with A record, it resulted in rn->cnlen
set and rn->u.cname overwritten by rn->u.addr (or rn->u.addrs), causing
segmentation fault later in ngx_resolver_free_node() on an attempt to free
overwritten rn->u.cname. The opposite (i.e. CNAME got after A) might cause
similar problems as well.
diff --git a/src/core/ngx_resolver.c b/src/core/ngx_resolver.c
index ecf97d7..edc43dc 100644
--- a/src/core/ngx_resolver.c
+++ b/src/core/ngx_resolver.c
@@ -513,8 +513,10 @@
/* lock alloc mutex */
- ngx_resolver_free_locked(r, rn->query);
- rn->query = NULL;
+ if (rn->query) {
+ ngx_resolver_free_locked(r, rn->query);
+ rn->query = NULL;
+ }
if (rn->cnlen) {
ngx_resolver_free_locked(r, rn->u.cname);
@@ -1409,6 +1411,9 @@
ngx_resolver_free(r, addrs);
}
+ ngx_resolver_free(r, rn->query);
+ rn->query = NULL;
+
return;
} else if (cname) {
@@ -1441,6 +1446,9 @@
(void) ngx_resolve_name_locked(r, ctx);
}
+ ngx_resolver_free(r, rn->query);
+ rn->query = NULL;
+
return;
}
