UBUNTU: SAUCE: apparmor4.0.0 [80/90]: apparmor: carry mediation check on label

BugLink: http://bugs.launchpad.net/bugs/2028253

In order to speed up the mediated check, precompute and store the
result as a bit per class type. This not only will allow us to
speed up the mediation check but is also a step to removing the
unconfined special cases as the unconfined check can be replaced
with the generic label_mediates() check.

need to compute initial profile mediated bit vector

Note: label check does not work for capabilities and resources

Signed-off-by: John Johansen <john.johansen@canonical.com>
(cherry picked from commit d8719977bc2bea2969846a49acfbabf06572ee1f
https://git.launchpad.net/~apparmor-dev/ubuntu-kernel-next)
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

security/apparmor/af_unix.c

@@ -47,7 +47,7 @@ static inline int unix_fs_perm(const char *op, u32 mask,
 	AA_BUG(!u);
 	AA_BUG(!UNIX_FS(aa_unix_sk(u)));
 
-	if (unconfined(label) || !LABEL_MEDIATES(label, AA_CLASS_FILE))
+	if (unconfined(label) || !label_mediates(label, AA_CLASS_FILE))
 		return 0;
 
 	mask &= NET_FS_PERMS;

security/apparmor/include/apparmor.h

@@ -38,6 +38,7 @@
 #define AA_CLASS_X		31
 #define AA_CLASS_DBUS		32
 
+/* NOTE: if AA_CLASS_LAST > 63 need to update label->mediates */
 #define AA_CLASS_LAST		AA_CLASS_DBUS
 
 /* Control parameters settable through module/boot flags */

security/apparmor/include/label.h

@@ -129,6 +129,7 @@ struct aa_label {
 	long flags;
 	u32 secid;
 	int size;
+	u64 mediates;
 	struct aa_profile *vec[];
 };
 
@@ -255,23 +256,17 @@ for ((I).i = (I).j = 0;							\
 #define fn_for_each_not_in_set(L1, L2, P, FN)				\
 	fn_for_each2_XXX((L1), (L2), P, FN, _not_in_set)
 
-#define LABEL_MEDIATES(L, C)						\
-({									\
-	struct aa_profile *profile;					\
-	struct label_it i;						\
-	int ret = 0;							\
-	label_for_each(i, (L), profile) {				\
-		struct aa_ruleset *rules =				\
-			list_first_entry(&profile->rules, typeof(*rules),\
-					 list);				\
-		if (RULE_MEDIATES(rules, (C))) {			\
-			ret = 1;					\
-			break;						\
-		}							\
-	}								\
-	ret;								\
-})
+static inline bool label_mediates(struct aa_label *L, unsigned char C)
+{
+	return (L)->mediates & (((u64) 1) << (C));
+}
 
+static inline bool label_mediates_safe(struct aa_label *L, unsigned char C)
+{
+	if (C > AA_CLASS_LAST)
+		return false;
+	return label_mediates(L, C);
+}
 
 int aa_label_cmp(struct aa_label *a, struct aa_label *b);
 void aa_labelset_destroy(struct aa_labelset *ls);

security/apparmor/include/policy.h

@@ -334,6 +334,19 @@ static inline aa_state_t ANY_RULE_MEDIATES(struct list_head *head,
 	return RULE_MEDIATES(rule, class);
 }
 
+void aa_compute_profile_mediates(struct aa_profile *profile);
+static inline bool profile_mediates(struct aa_profile *profile,
+				    unsigned char class)
+{
+	return label_mediates(&profile->label, class);
+}
+
+static inline bool profile_mediates_safe(struct aa_profile *profile,
+					 unsigned char class)
+{
+	return label_mediates_safe(&profile->label, class);
+}
+
 /**
  * aa_get_profile - increment refcount on profile @p
  * @p: profile  (MAYBE NULL)

security/apparmor/label.c

@@ -198,21 +198,25 @@ static bool vec_is_stale(struct aa_profile **vec, int n)
 	return false;
 }
 
-static long accum_vec_flags(struct aa_profile **vec, int n)
+static void accum_label_info(struct aa_label *new)
 {
 	long u = FLAG_UNCONFINED;
 	int i;
 
-	AA_BUG(!vec);
+	AA_BUG(!new->vec);
 
-	for (i = 0; i < n; i++) {
-		u |= vec[i]->label.flags & (FLAG_DEBUG1 | FLAG_DEBUG2 |
-					    FLAG_STALE);
-		if (!(u & vec[i]->label.flags & FLAG_UNCONFINED))
+	/* size == 1 is a profile and flags must be set as part of creation */
+	if (new->size == 1)
+	       return;
+
+       for (i = 0; i < new->size; i++) {
+		u |= new->vec[i]->label.flags & (FLAG_DEBUG1 | FLAG_DEBUG2 |
+						 FLAG_STALE);
+		if (!(u & new->vec[i]->label.flags & FLAG_UNCONFINED))
 			u &= ~FLAG_UNCONFINED;
+		new->mediates |= new->vec[i]->label.mediates;
 	}
-
-	return u;
+	new->flags |= u;
 }
 
 static int sort_cmp(const void *a, const void *b)
@@ -645,7 +649,7 @@ static bool __label_replace(struct aa_label *old, struct aa_label *new)
 		rb_replace_node(&old->node, &new->node, &ls->root);
 		old->flags &= ~FLAG_IN_TREE;
 		new->flags |= FLAG_IN_TREE;
-		new->flags |= accum_vec_flags(new->vec, new->size);
+		accum_label_info(new);
 		return true;
 	}
 
@@ -706,7 +710,7 @@ static struct aa_label *__label_insert(struct aa_labelset *ls,
 	rb_link_node(&label->node, parent, new);
 	rb_insert_color(&label->node, &ls->root);
 	label->flags |= FLAG_IN_TREE;
-	label->flags |= accum_vec_flags(label->vec, label->size);
+	accum_label_info(label);
 
 	return aa_get_label(label);
 }

security/apparmor/lsm.c

@@ -1251,7 +1251,7 @@ static int apparmor_userns_create(const struct cred *cred)
 	label = begin_current_label_crit_section();
 	/* remove unprivileged_userns_restricted check when unconfined is updated */
 	if (aa_unprivileged_userns_restricted ||
-	    LABEL_MEDIATES(label, AA_CLASS_NS)) {
+	    label_mediates(label, AA_CLASS_NS)) {
 		DEFINE_AUDIT_DATA(ad, LSM_AUDIT_DATA_TASK, AA_CLASS_NS,
 				  OP_USERNS_CREATE);
 		ad.subj_cred = current_cred();

security/apparmor/policy.c

@@ -382,6 +382,30 @@ fail:
 	return NULL;
 }
 
+/* set of rules that are mediated by unconfined */
+static int unconfined_mediates[] = { AA_CLASS_NS, AA_CLASS_IO_URING, 0 };
+
+/* must be called after profile rulesets and start information is setup */
+void aa_compute_profile_mediates(struct aa_profile *profile)
+{
+	int c;
+
+	if (profile_unconfined(profile)) {
+		int *pos;
+
+		for (pos = unconfined_mediates; *pos; pos++) {
+			if (ANY_RULE_MEDIATES(&profile->rules, AA_CLASS_NS) !=
+			    DFA_NOMATCH)
+				profile->label.mediates |= ((u64) 1) << AA_CLASS_NS;
+		}
+		return;
+	}
+	for (c = 0; c <= AA_CLASS_LAST; c++) {
+		if (ANY_RULE_MEDIATES(&profile->rules, c) != DFA_NOMATCH)
+			profile->label.mediates |= ((u64) 1) << c;
+	}
+}
+
 /* TODO: profile accounting - setup in remove */
 
 /**
@@ -637,10 +661,12 @@ struct aa_profile *aa_alloc_null(struct aa_profile *parent, const char *name,
 	rules = list_first_entry(&profile->rules, typeof(*rules), list);
 	rules->file = aa_get_pdb(nullpdb);
 	rules->policy = aa_get_pdb(nullpdb);
+	aa_compute_profile_mediates(profile);
 
 	if (parent) {
 		profile->path_flags = parent->path_flags;
-
+		/* override/inherit what is mediated from parent */
+		profile->label.mediates = parent->label.mediates;
 		/* released on free_profile */
 		rcu_assign_pointer(profile->parent, aa_get_profile(parent));
 		profile->ns = aa_get_ns(parent->ns);

security/apparmor/policy_unpack.c

@@ -1144,6 +1144,8 @@ static struct aa_profile *unpack_profile(struct aa_ext *e, char **ns_name)
 		goto fail;
 	}
 
+	aa_compute_profile_mediates(profile);
+
 	return profile;
 
 fail: