ima: fix ima_inode_post_setattr

Changing file metadata (eg. uid, guid) could result in having to
re-appraise a file's integrity, but does not change the "new file"
status nor the security.ima xattr.  The IMA_PERMIT_DIRECTIO and
IMA_DIGSIG_REQUIRED flags are policy rule specific.  This patch
only resets these flags, not the IMA_NEW_FILE or IMA_DIGSIG flags.

With this patch, changing the file timestamp will not remove the
file signature on new files.
Reported-by: Dmitry Rozhkov <dmitry.rozhkov@linux.intel.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Tested-by: Dmitry Rozhkov <dmitry.rozhkov@linux.intel.com>

security/integrity/ima/ima_appraise.c

@@ -328,7 +328,7 @@ void ima_inode_post_setattr(struct dentry *dentry)
 	if (iint) {
 		iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
 				 IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
-				 IMA_ACTION_FLAGS);
+				 IMA_ACTION_RULE_FLAGS);
 		if (must_appraise)
 			iint->flags |= IMA_APPRAISE;
 	}

security/integrity/integrity.h

@@ -28,6 +28,7 @@
 
 /* iint cache flags */
 #define IMA_ACTION_FLAGS	0xff000000
+#define IMA_ACTION_RULE_FLAGS	0x06000000
 #define IMA_DIGSIG		0x01000000
 #define IMA_DIGSIG_REQUIRED	0x02000000
 #define IMA_PERMIT_DIRECTIO	0x04000000