Commit 
8aac4cc3a9d7 ("IB/qib: RCU locking for MR validation") introduced
a bug that broke user post sends.  The proper validation of the MR
was lost in the patch.
This patch corrects that validation.
Reviewed-by: Dean Luick <dean.luick@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Roland Dreier <roland@purestorage.com>
                goto bail;
 
        off = sge->addr - mr->user_base;
-       if (unlikely(sge->addr < mr->iova || off + sge->length > mr->length ||
-                    (mr->access_flags & acc) == 0))
+       if (unlikely(sge->addr < mr->user_base ||
+                    off + sge->length > mr->length ||
+                    (mr->access_flags & acc) != acc))
                goto bail;
        if (unlikely(!atomic_inc_not_zero(&mr->refcount)))
                goto bail;