messages/MOSDPing: fix the inflation amount calculation

If user specifies a min_message_size small enough (or zero to disable
it altogether), OSDs will crash and burn while trying to allocate
almost 4GB of payload (both min_message_size and payload.length() are
unsigned, so it'll roll over back to 4GB and MAX(4GB, 0) will use 4GB).
If the size of dummy payload is 0, don't bother constructing bufferptr
and bufferlist, then encoding that.

Signed-off-by: Piotr Dałek <piotr.dalek@corp.ovh.com>
(cherry picked from commit d959735a7d684018df564573a2ff88092d870fc1)

diff --git a/src/messages/MOSDPing.h b/src/messages/MOSDPing.h
index cf211ed9795c0954931dac7681313b2900032591..8a02001eaedfd31fad7157b6e844c63beda9c6f9 100644 (file)
--- a/src/messages/MOSDPing.h
+++ b/src/messages/MOSDPing.h
@@ -100,21 +100,26 @@ public:
     ::encode(peer_stat, payload);
     ::encode(stamp, payload);
 
-    bufferlist pad;
-    size_t s = MAX(min_message_size - payload.length(), 0);
-    // this should be big enough for normal min_message padding sizes. since
-    // we are targetting jumbo ethernet frames around 9000 bytes, 16k should
-    // be more than sufficient!  the compiler will statically zero this so
-    // that at runtime we are only adding a bufferptr reference to it.
-    static char zeros[16384] = {};
-    while (s > sizeof(zeros)) {
-      pad.append(buffer::create_static(sizeof(zeros), zeros));
-      s -= sizeof(zeros);
-    }
+    size_t s = 0;
+    if (min_message_size > payload.length())
+      s = min_message_size - payload.length();
+    ::encode((uint32_t)s, payload);
     if (s) {
-      pad.append(buffer::create_static(s, zeros));
+      bufferlist pad;
+      // this should be big enough for normal min_message padding sizes. since
+      // we are targetting jumbo ethernet frames around 9000 bytes, 16k should
+      // be more than sufficient!  the compiler will statically zero this so
+      // that at runtime we are only adding a bufferptr reference to it.
+      static char zeros[16384] = {};
+      while (s > sizeof(zeros)) {
+       pad.append(buffer::create_static(sizeof(zeros), zeros));
+       s -= sizeof(zeros);
+      }
+      if (s) {
+       pad.append(buffer::create_static(s, zeros));
+      }
+      ::encode(pad, payload);
     }
-    ::encode(pad, payload);
   }
 
   const char *get_type_name() const { return "osd_ping"; }