cls/rgw: test before accessing pkeys->rbegin()

if pkeys is empty here, dereferencing rbegin() will crash

Fixes: http://tracker.ceph.com/issues/39984
Signed-off-by: Casey Bodley <cbodley@redhat.com>
(cherry picked from commit a936a06a657ce1cc118d75f66773aeda4167bbf3)

diff --git a/src/cls/rgw/cls_rgw.cc b/src/cls/rgw/cls_rgw.cc
index 6b21ad1d6afa571e60a0c53480c1d75c5bf2b515..2091914ea6eda4abe4a3aa5eca5fa5315fc3567f 100644 (file)
--- a/src/cls/rgw/cls_rgw.cc
+++ b/src/cls/rgw/cls_rgw.cc
@@ -176,7 +176,7 @@ static int get_obj_vals(cls_method_context_t hctx, const string& start, const st
   if (num_entries == (int)pkeys->size() || !(*pmore))
     return 0;
 
-  if (pkeys->rbegin()->first > new_start) {
+  if (pkeys->size() && new_start < pkeys->rbegin()->first) {
     new_start = pkeys->rbegin()->first;
   }