From e0f90f03ddf2824b448f6affc34ed40d4cead5d2 Mon Sep 17 00:00:00 2001
From: Jason Dillaman <dillaman@redhat.com>
Date: Thu, 26 Jan 2017 14:02:11 -0500
Subject: [PATCH] librbd: introduce new constants for tracking max block name
 prefix

Fixes: http://tracker.ceph.com/issues/18653
Signed-off-by: Jason Dillaman <dillaman@redhat.com>
(cherry picked from commit 2c08629c99d90aa7676b59263c055c9f1f577039)
---
 src/include/rbd_types.h           | 19 +++++++++++++++++++
 src/librbd/Utils.cc               |  5 ++---
 src/librbd/image/CreateRequest.cc |  5 +++++
 3 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/include/rbd_types.h b/src/include/rbd_types.h
index de7d1c6f35a8b..a8eac71538e1d 100644
--- a/src/include/rbd_types.h
+++ b/src/include/rbd_types.h
@@ -67,6 +67,25 @@
 #define RBD_MAX_OBJ_NAME_SIZE	96
 #define RBD_MAX_BLOCK_NAME_SIZE 24
 
+/**
+ * Maximum string length of the RBD v2 image id (not including
+ * null termination). This limit was derived from the existing
+ * RBD_MAX_BLOCK_NAME_SIZE limit which needs to hold the "rbd_data."
+ * prefix and null termination.
+ */
+#define RBD_MAX_IMAGE_ID_LENGTH 14
+
+/**
+ * Maximum string length of the RBD block object name prefix (not including
+ * null termination).
+ *
+ * v1 format: rb.<max 8-byte high id>.<max 8-byte low id>.<max 8-byte extra>
+ * v2 format: rbd_data.[<max 19-byte pool id>.]<max 14-byte image id>
+ *
+ * Note: new features might require increasing this maximum prefix length.
+ */
+#define RBD_MAX_BLOCK_NAME_PREFIX_LENGTH 43
+
 #define RBD_COMP_NONE		0
 #define RBD_CRYPT_NONE		0
 
diff --git a/src/librbd/Utils.cc b/src/librbd/Utils.cc
index 1dff4ce4b8f1d..9dcead61f63ff 100644
--- a/src/librbd/Utils.cc
+++ b/src/librbd/Utils.cc
@@ -56,9 +56,8 @@ std::string generate_image_id(librados::IoCtx &ioctx) {
   std::string id = bid_ss.str();
 
   // ensure the image id won't overflow the fixed block name size
-  const size_t max_id_length = RBD_MAX_BLOCK_NAME_SIZE - strlen(RBD_DATA_PREFIX) - 1;
-  if (id.length() > max_id_length) {
-    id = id.substr(id.length() - max_id_length);
+  if (id.length() > RBD_MAX_IMAGE_ID_LENGTH) {
+    id = id.substr(id.length() - RBD_MAX_IMAGE_ID_LENGTH);
   }
 
   return id;
diff --git a/src/librbd/image/CreateRequest.cc b/src/librbd/image/CreateRequest.cc
index 2a9dfac2fc1f2..2c10092723ede 100644
--- a/src/librbd/image/CreateRequest.cc
+++ b/src/librbd/image/CreateRequest.cc
@@ -443,6 +443,11 @@ void CreateRequest<I>::create_image() {
     oss << stringify(m_ioctx.get_id()) << ".";
   }
   oss << m_image_id;
+  if (oss.str().length() > RBD_MAX_BLOCK_NAME_PREFIX_LENGTH) {
+    lderr(m_cct) << "object prefix '" << oss.str() << "' too large" << dendl;
+    complete(-EINVAL);
+    return;
+  }
 
   librados::ObjectWriteOperation op;
   op.create(true);
-- 
2.39.5