  A new calculation of the $\bar{p}/p$ ratio in cosmic rays is compared to the
recent PAMELA data. The good match up to 100 GeV allows to set constraints on
exotic contributions from thermal WIMP dark matter candidates. We derive
stringent limits on possible enhancements of the WIMP \pbar flux: a $m_{\rm
WIMP}$=100 GeV (1 TeV) signal cannot be increased by more than a factor 6 (40)
without overrunning PAMELA data. Annihilation through the $W^+W^-$ channel is
also inspected and cross-checked with $e^+/(e^-+e^+)$ data. This scenario is
strongly disfavored as it fails to simultaneously reproduce positron and
antiproton measurements.
