rgw: fix FP error when calculating enteries per bi shard

When calculating how many entries per shard to request during an
ordered bucket listing, we divide by the number of bucket index
shards. If this value is 0, then a floating point exception is
generated, crashing the RGW.

This addresses the proximate issue by detecting the situation and
returning an error rather than crashing.

Signed-off-by: J. Eric Ivancich <ivancich@redhat.com>

diff --git a/src/rgw/rgw_rados.cc b/src/rgw/rgw_rados.cc
index c5e5d53a3df4766f8fcdea366b70d8a25afe533a..15fbe3d0ab122c53cb82a56909adbb6c4a8dcdf1 100644 (file)
--- a/src/rgw/rgw_rados.cc
+++ b/src/rgw/rgw_rados.cc
@@ -8534,9 +8534,16 @@ int RGWRados::cls_obj_set_bucket_tag_timeout(const DoutPrefixProvider *dpp, RGWB
 }
 
 
+// returns 0 if there is an error in calculation
 uint32_t RGWRados::calc_ordered_bucket_list_per_shard(uint32_t num_entries,
                                                      uint32_t num_shards)
 {
+  if (num_shards == 0) {
+    // we'll get a floating point exception since we divide by
+    // num_shards
+    return 0;
+  }
+
   // We want to minimize the chances that when num_shards >>
   // num_entries that we return much fewer than num_entries to the
   // client. Given all the overhead of making a cls call to the osd,
@@ -8618,6 +8625,13 @@ int RGWRados::cls_bucket_list_ordered(const DoutPrefixProvider *dpp,
   }
 
   const uint32_t shard_count = shard_oids.size();
+  if (shard_count == 0) {
+    ldpp_dout(dpp, 0) << "ERROR: " << __func__ <<
+      ": the bucket index shard count appears to be 0, "
+      "which is an illegal value" << dendl;
+    return -ERR_INVALID_BUCKET_STATE;
+  }
+
   uint32_t num_entries_per_shard;
   if (expansion_factor == 0) {
     num_entries_per_shard =
@@ -8632,6 +8646,13 @@ int RGWRados::cls_bucket_list_ordered(const DoutPrefixProvider *dpp,
     num_entries_per_shard = num_entries;
   }
 
+  if (num_entries_per_shard == 0) {
+    ldpp_dout(dpp, 0) << "ERROR: " << __func__ <<
+      ": unable to calculate the number of entries to read from each "
+      "bucket index shard" << dendl;
+    return -ERR_INVALID_BUCKET_STATE;
+  }
+
   ldpp_dout(dpp, 10) << __func__ <<
     ": request from each of " << shard_count <<
     " shard(s) for " << num_entries_per_shard << " entries to get " <<