[PATCH] allow audit filtering on bit & operations

Right now the audit filter can match on = != > < >= blah blah blah.
This allow the filter to also look at bitwise AND operations, &

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/audit.h

@@ -161,7 +161,7 @@
  * are currently used in an audit field constant understood by the kernel.
  * If you are adding a new #define AUDIT_<whatever>, please ensure that
  * AUDIT_UNUSED_BITS is updated if need be. */
-#define AUDIT_UNUSED_BITS	0x0FFFFC00
+#define AUDIT_UNUSED_BITS	0x07FFFC00
 
 
 /* Rule fields */
@@ -213,25 +213,29 @@
 #define AUDIT_NEGATE			0x80000000
 
 /* These are the supported operators.
- *	4  2  1
- *	=  >  <
- *	-------
- *	0  0  0		0	nonsense
- *	0  0  1		1	<
- *	0  1  0		2	>
- *	0  1  1		3	!=
- *	1  0  0		4	=
- *	1  0  1		5	<=
- *	1  1  0		6	>=
- *	1  1  1		7	all operators
+ *	4  2  1  8
+ *	=  >  <  ?
+ *	----------
+ *	0  0  0	 0	00	nonsense
+ *	0  0  0	 1	08	&  bit mask
+ *	0  0  1	 0	10	<
+ *	0  1  0	 0	20	>
+ *	0  1  1	 0	30	!=
+ *	1  0  0	 0	40	=
+ *	1  0  0	 1	48	&=  bit test
+ *	1  0  1	 0	50	<=
+ *	1  1  0	 0	60	>=
+ *	1  1  1	 1	78	all operators
  */
+#define AUDIT_BIT_MASK			0x08000000
 #define AUDIT_LESS_THAN			0x10000000
 #define AUDIT_GREATER_THAN		0x20000000
 #define AUDIT_NOT_EQUAL			0x30000000
 #define AUDIT_EQUAL			0x40000000
+#define AUDIT_BIT_TEST			(AUDIT_BIT_MASK|AUDIT_EQUAL)
 #define AUDIT_LESS_THAN_OR_EQUAL	(AUDIT_LESS_THAN|AUDIT_EQUAL)
 #define AUDIT_GREATER_THAN_OR_EQUAL	(AUDIT_GREATER_THAN|AUDIT_EQUAL)
-#define AUDIT_OPERATORS			(AUDIT_EQUAL|AUDIT_NOT_EQUAL)
+#define AUDIT_OPERATORS			(AUDIT_EQUAL|AUDIT_NOT_EQUAL|AUDIT_BIT_MASK)
 
 /* Status symbols */
 				/* Mask values */

kernel/auditfilter.c

@@ -456,6 +456,13 @@ static struct audit_entry *audit_rule_to_entry(struct audit_rule *rule)
 		case AUDIT_DEVMINOR:
 		case AUDIT_EXIT:
 		case AUDIT_SUCCESS:
+			/* bit ops are only useful on syscall args */
+			if (f->op == AUDIT_BIT_MASK ||
+						f->op == AUDIT_BIT_TEST) {
+				err = -EINVAL;
+				goto exit_free;
+			}
+			break;
 		case AUDIT_ARG0:
 		case AUDIT_ARG1:
 		case AUDIT_ARG2:
@@ -1566,6 +1573,10 @@ int audit_comparator(const u32 left, const u32 op, const u32 right)
 		return (left > right);
 	case AUDIT_GREATER_THAN_OR_EQUAL:
 		return (left >= right);
+	case AUDIT_BIT_MASK:
+		return (left & right);
+	case AUDIT_BIT_TEST:
+		return ((left & right) == right);
 	}
 	BUG();
 	return 0;