Are you already in US , if not try to correct your visa stamp .
Even i was in same boat , I797 valid till feb 2014, and visa was stamped till dec 2014
At the port of entry I was given I 94 till dec 2014, which created many problems.
Attorneys told I94 should be valid till end of work permit so that they can extend work permit 6 months prior to I 94 expiry.
So, I went to local CBP and got it corrected. They were reluctant to change it but with great difficulty finally changed I94 date till feb 2014. Now I can apply for extension.
So, remember that work permit can be extended on the basis of I94. Getting I94 date as per visa may allow to legally stay in the country BUT NOT WORK as your work permit expires before that.
So, if you cannot change passport visa, [b]atleast show I797 at port of entry and get the correct I94[/b] and extend work permit based on that.
I hope you will not have to go through the hassle of dealing with customs and border protection once you are inside the country.