If the graviton has mass, then it presumably can generate its own gravity. Thus, gravity would create gravity. This might require a significant rethinking of physics.

Gravity contains energy, so via mass/energy equivalence, already creates gravity, according to some scientists.

http://www.einstein-online.info/spotlights/gravity_of_gravityThe important thing to remember is that mass and energy are not created.

If M is the original mass/energy that creates gravity,

And G is the gravity (curvature) created by M,

Then, although G carries energy, the total mass/energy of M + G cannot be greater than the original mass/energy of M.

We might continue this line of thought by saying that the energy in G gives rise to more gravity (G2), but the total still remains the same: the mass/energy of M + G1 + G2 cannot be greater than the mass/energy of M.

The same reasoning must apply in the unlikely event that the graviton has mass.