Avoid some undefined pointer arithmetic

Avoid some undefined pointer arithmetic

A common idiom in the codebase is:

 if (p + len > limit)
 {
     return; /* Too long */
 }

 Where "p" points to some malloc'd data of SIZE bytes and
 limit == p + SIZE

 "len" here could be from some externally supplied data (e.g. from a TLS
 message).

 The rules of C pointer arithmetic are such that "p + len" is only well
 defined where len <= SIZE. Therefore the above idiom is actually
 undefined behaviour.

 For example this could cause problems if some malloc implementation
 provides an address for "p" such that "p + len" actually overflows for
 values of len that are too big and therefore p + len < limit!w

Change-Id: Iafd9f2d3c35eb26b930a45b5a9461cb19f75bcb4
Signed-off-by: min7.choi <min7.choi@samsung.com>