ima: change integrity cache to store measured pcr

IMA avoids re-measuring files by storing the current state as a flag in
the integrity cache. It will then skip adding a new measurement log entry
if the cache reports the file as already measured.

If a policy measures an already measured file to a new PCR, the measurement
will not be added to the list. This patch implements a new bitfield for
specifying which PCR the file was measured into, rather than if it was
measured.

Signed-off-by: Eric Richter <erichte@linux.vnet.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

security/integrity/ima/ima_appraise.c

@@ -370,6 +370,7 @@ static void ima_reset_appraise_flags(struct inode *inode, int digsig)
 		return;
 
 	iint->flags &= ~IMA_DONE_MASK;
+	iint->measured_pcrs = 0;
 	if (digsig)
 		iint->flags |= IMA_DIGSIG;
 	return;