ima: update builtin policies

This patch defines a builtin measurement policy "tcb", similar to the
existing "ima_tcb", but with additional rules to also measure files
based on the effective uid and to measure files opened with the "read"
mode bit set (eg. read, read-write).

Changing the builtin "ima_tcb" policy could potentially break existing
users.  Instead of defining a new separate boot command line option each
time the builtin measurement policy is modified, this patch defines a
single generic boot command line option "ima_policy=" to specify the
builtin policy and deprecates the use of the builtin ima_tcb policy.

[The "ima_policy=" boot command line option is based on Roberto Sassu's
"ima: added new policy type exec" patch.]

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Dr. Greg Wettstein <gw@idfusion.org>
Cc: stable@vger.kernel.org

Documentation/kernel-parameters.txt

@@ -1398,7 +1398,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			The list of supported hash algorithms is defined
 			in crypto/hash_info.h.
 
-	ima_tcb		[IMA]
+	ima_policy=	[IMA]
+			The builtin measurement policy to load during IMA
+			setup.  Specyfing "tcb" as the value, measures all
+			programs exec'd, files mmap'd for exec, and all files
+			opened with the read mode bit set by either the
+			effective uid (euid=0) or uid=0.
+			Format: "tcb"
+
+	ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
 			Load a policy which meets the needs of the Trusted
 			Computing Base.  This means IMA will measure all
 			programs exec'd, files mmap'd for exec, and all files