commit 42729454d3a69ae30694646dc5a95737b887b829
Author: Josh Stone <jistone@redhat.com>
Date:   Fri Sep 9 14:27:49 2016 -0700

    RT: trymmap should retry if the result is out of range
    
    An address passed to `mmap` is just taken as a hint, and the OS may
    return something wildly different if that address is not available.
    This is undesirable when we're trying to create a constrained alloc.
    
    Now we will check that the address is in the requested range before
    accepting it.  Otherwise, unmap it and try a new hint.

diff --git a/dyninstAPI_RT/src/RTheap.c b/dyninstAPI_RT/src/RTheap.c
index eae69700d3ef..ddb4a363bf25 100644
--- a/dyninstAPI_RT/src/RTheap.c
+++ b/dyninstAPI_RT/src/RTheap.c
@@ -128,8 +128,13 @@ static Address trymmap(size_t len, Address beg, Address end, size_t inc, int fd)
   /* until we get one that succeeds.*/
   for (addr = beg; addr + len <= end; addr += inc) {
     result = map_region((void *) addr, len, fd);
-    if (result)
+    if (result) {
+      /* Success doesn't necessarily mean it actually mapped at the hinted
+       * address.  Return if it's in range, else unmap and try again. */
+      if ((Address) result >= beg && (Address) result + len <= end)
         return (Address) result;
+      unmap_region(result, len);
+    }
   }
   return (Address) NULL;
 }