Fix: Integer overflowed argument

Fix: Integer overflowed argument

Found by Coverity:

CID 1242317 (#1 of 2): Integer overflowed argument (INTEGER_OVERFLOW)25.
overflow_sink: Overflowed or truncated value (or a value computed from
an overflowed or truncated value) new_nbmem * 304UL used as critical
argument to function.

CID 1242317 (#2 of 2): Integer overflowed argument (INTEGER_OVERFLOW)27.
overflow_sink: Overflowed or truncated value (or a value computed from
an overflowed or truncated value) (new_nbmem - nbmem) * 304UL used as
critical argument to function.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>