apparmor: make sure perm indexes are accumulated

accumulate permission indexes on a first encountered basis. This
favors original rulesets so that new ones can not override without
profile replacement.
Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/include/file.h

@@ -88,10 +88,10 @@ static inline struct aa_label *aa_get_file_label(struct aa_file_ctx *ctx)
  * - exec type - which determines how the executable name and index are used
  * - flags - which modify how the destination name is applied
  */
-#define AA_X_INDEX_MASK		0x00ffffff
+#define AA_X_INDEX_MASK		AA_INDEX_MASK
 
 #define AA_X_TYPE_MASK		0x0c000000
-#define AA_X_NONE		0x00000000
+#define AA_X_NONE		AA_INDEX_NONE
 #define AA_X_NAME		0x04000000 /* use executable name px */
 #define AA_X_TABLE		0x08000000 /* use a specified name ->n# */
 

security/apparmor/include/perms.h

@@ -78,11 +78,20 @@ struct aa_perms {
 	u32 quiet;	/* set only when ~allow | deny */
 	u32 hide;	/* set only when  ~allow | deny */
 
+
 	u32 xindex;
 	u32 tag;	/* tag string index, if present */
 	u32 label;	/* label string index, if present */
 };
 
+/*
+ * Indexes are broken into a 24 bit index and 8 bit flag.
+ * For the index to be valid there must be a value in the flag
+ */
+#define AA_INDEX_MASK			0x00ffffff
+#define AA_INDEX_FLAG_MASK		0xff000000
+#define AA_INDEX_NONE			0
+
 #define ALL_PERMS_MASK 0xffffffff
 extern struct aa_perms nullperms;
 extern struct aa_perms allperms;

security/apparmor/lib.c

@@ -348,6 +348,13 @@ void aa_perms_accum_raw(struct aa_perms *accum, struct aa_perms *addend)
 	accum->hide &= addend->hide & ~addend->allow;
 	accum->prompt |= addend->prompt & ~addend->allow & ~addend->deny;
 	accum->subtree |= addend->subtree & ~addend->deny;
+
+	if (!accum->xindex)
+		accum->xindex = addend->xindex;
+	if (!accum->tag)
+		accum->tag = addend->tag;
+	if (!accum->label)
+		accum->label = addend->label;
 }
 
 /**
@@ -367,6 +374,13 @@ void aa_perms_accum(struct aa_perms *accum, struct aa_perms *addend)
 	accum->hide &= addend->hide & ~accum->allow;
 	accum->prompt |= addend->prompt & ~accum->allow & ~accum->deny;
 	accum->subtree &= addend->subtree & ~accum->deny;
+
+	if (!accum->xindex)
+		accum->xindex = addend->xindex;
+	if (!accum->tag)
+		accum->tag = addend->tag;
+	if (!accum->label)
+		accum->label = addend->label;
 }
 
 void aa_profile_match_label(struct aa_profile *profile, struct aa_label *label,