The firewall verified gather buffers before copying them. This
allowed a malicious application to rewrite the buffer content by
timing the rewrite carefully.

This patch makes the buffer validation occur after copying the
buffers.
Signed-off-by: NArto Merilainen <amerilainen@nvidia.com>
Signed-off-by: NTerje Bergstrom <tbergstrom@nvidia.com>
Signed-off-by: NThierry Reding <thierry.reding@gmail.com>