ima: forbid write access to files with digital signatures

This patch forbids write access to files with digital signatures, as they
are considered immutable.

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

diff --cc security/integrity/ima/ima_main.c
Simple merge