[PATCH userspace v2 6/7] [RFC] lisepol: slightly more thorough optimization

[Ondrej Mosnacek <omosnace@xxxxxxxxxx>]

Removes also rules that are covered only by a union of two or more
rules. There are usually only a few of such rules (if any), but there
should be almost no (policy build) perfomance cost for this.

Side effect: clears all permission bits covered by a more general rule
-> might slow down avtab lookups (only a single rule will now match each
query)
---
 libsepol/src/optimize.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/libsepol/src/optimize.c b/libsepol/src/optimize.c
index b3859b6c..abb711e7 100644
--- a/libsepol/src/optimize.c
+++ b/libsepol/src/optimize.c
@@ -73,36 +73,38 @@ static void destroy_type_map(const policydb_t *p, ebitmap_t *type_map)
 	free(type_map);
 }
 
-static int match_xperms(const uint32_t *p1, const uint32_t *p2)
+static int process_xperms(uint32_t *p1, const uint32_t *p2)
 {
 	size_t i;
+	int ret = 1;
 
 	for (i = 0; i < EXTENDED_PERMS_LEN; i++) {
-		if ((p2[i] & p1[i]) != p1[i])
-			return 0;
+		p1[i] &= ~p2[i];
+		if (p1[i] != 0)
+			ret = 0;
 	}
-	return 1;
+	return ret;
 }
 
-static int match_avtab_datum(uint16_t specified,
-			     const avtab_datum_t *d1, const avtab_datum_t *d2)
+static int process_avtab_datum(uint16_t specified,
+			       avtab_datum_t *d1, const avtab_datum_t *d2)
 {
 	/* inverse logic needed for AUDITDENY rules */
 	if (specified & AVTAB_AUDITDENY)
-		return (d1->data & d2->data) == d2->data;
+		return (d1->data |= ~d2->data) == 0xFFFFFFFF;
 
 	if (specified & AVTAB_AV)
-		return (d2->data & d1->data) == d1->data;
+		return (d1->data &= ~d2->data) == 0;
 
 	if (specified & AVTAB_XPERMS) {
-		const avtab_extended_perms_t *x1 = d1->xperms;
+		avtab_extended_perms_t *x1 = d1->xperms;
 		const avtab_extended_perms_t *x2 = d2->xperms;
 
 		if (x1->specified == AVTAB_XPERMS_IOCTLFUNCTION) {
 			if (x2->specified == AVTAB_XPERMS_IOCTLFUNCTION) {
 				if (x1->driver != x2->driver)
 					return 0;
-				return match_xperms(x1->perms, x2->perms);
+				return process_xperms(x1->perms, x2->perms);
 			}
 			if (x2->specified == AVTAB_XPERMS_IOCTLDRIVER)
 				return xperm_test(x1->driver, x2->perms);
@@ -111,7 +113,7 @@ static int match_avtab_datum(uint16_t specified,
 				return 0;
 
 			if (x2->specified == AVTAB_XPERMS_IOCTLDRIVER)
-				return match_xperms(x1->perms, x2->perms);
+				return process_xperms(x1->perms, x2->perms);
 		}
 		return 0;
 	}
@@ -152,7 +154,7 @@ static int is_avrule_redundant(avtab_ptr_t entry, avtab_t *tab,
 			if (!d2)
 				continue;
 
-			if (match_avtab_datum(key.specified, d1, d2))
+			if (process_avtab_datum(key.specified, d1, d2))
 				return 1;
 		}
 	}
@@ -205,7 +207,7 @@ static int is_cond_rule_redundant(avtab_ptr_t e1, cond_av_list_t *list,
 		if (!ebitmap_get_bit(&type_map[t1], t2))
 			continue;
 
-		if (match_avtab_datum(k1, &e1->datum, &e2->datum))
+		if (process_avtab_datum(k1, &e1->datum, &e2->datum))
 			return 1;
 	}
 	return 0;
-- 
2.20.1