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>
(cherry picked from commit bd6ee7e78d857bff31b0bb23f0ee8d8737ffef8e)

Conflicts:
	src/rgw/rgw_rados.cc (trivial: __func__ vs __PRETTY_FUNCTION__)

diff --git a/src/rgw/rgw_rados.cc b/src/rgw/rgw_rados.cc
index 958fe5d4538faec73da0bf44b8d04c92c4049471..2fbe0471d57b638ded8a443bc3c51914495024db 100644 (file)
--- a/src/rgw/rgw_rados.cc
+++ b/src/rgw/rgw_rados.cc
@@ -8643,9 +8643,16 @@ 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,
@@ -8723,6 +8730,13 @@ 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 =
@@ -8737,6 +8751,13 @@ 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) << __PRETTY_FUNCTION__ <<
     ": request from each of " << shard_count <<
     " shard(s) for " << num_entries_per_shard << " entries to get " <<