apparmor: share profile name on replacement

The profile names are the same, leverage this.
Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/include/lib.h

@@ -100,6 +100,36 @@ static inline bool path_mediated_fs(struct dentry *dentry)
 	return !(dentry->d_sb->s_flags & MS_NOUSER);
 }
 
+
+struct counted_str {
+	struct kref count;
+	char name[];
+};
+
+#define str_to_counted(str) \
+	((struct counted_str *)(str - offsetof(struct counted_str, name)))
+
+#define __counted	/* atm just a notation */
+
+void aa_str_kref(struct kref *kref);
+char *aa_str_alloc(int size, gfp_t gfp);
+
+
+static inline __counted char *aa_get_str(__counted char *str)
+{
+	if (str)
+		kref_get(&(str_to_counted(str)->count));
+
+	return str;
+}
+
+static inline void aa_put_str(__counted char *str)
+{
+	if (str)
+		kref_put(&str_to_counted(str)->count, aa_str_kref);
+}
+
+
 /* struct aa_policy - common part of both namespaces and profiles
  * @name: name of the object
  * @hname - The hierarchical name
@@ -108,7 +138,7 @@ static inline bool path_mediated_fs(struct dentry *dentry)
  */
 struct aa_policy {
 	const char *name;
-	const char *hname;
+	__counted char *hname;
 	struct list_head list;
 	struct list_head profiles;
 };

security/apparmor/lib.c

@@ -134,6 +134,24 @@ void aa_info_message(const char *str)
 	printk(KERN_INFO "AppArmor: %s\n", str);
 }
 
+__counted char *aa_str_alloc(int size, gfp_t gfp)
+{
+	struct counted_str *str;
+
+	str = kmalloc(sizeof(struct counted_str) + size, gfp);
+	if (!str)
+		return NULL;
+
+	kref_init(&str->count);
+	return str->name;
+}
+
+void aa_str_kref(struct kref *kref)
+{
+	kfree(container_of(kref, struct counted_str, count));
+}
+
+
 const char aa_file_perm_chrs[] = "xwracd         km l     ";
 const char *aa_file_perm_names[] = {
 	"exec",
@@ -296,6 +314,7 @@ void aa_compute_perms(struct aa_dfa *dfa, unsigned int state,
  * @policy: policy to initialize  (NOT NULL)
  * @prefix: prefix name if any is required.  (MAYBE NULL)
  * @name: name of the policy, init will make a copy of it  (NOT NULL)
+ * @gfp: allocation mode
  *
  * Note: this fn creates a copy of strings passed in
  *
@@ -304,16 +323,21 @@ void aa_compute_perms(struct aa_dfa *dfa, unsigned int state,
 bool aa_policy_init(struct aa_policy *policy, const char *prefix,
 		    const char *name, gfp_t gfp)
 {
+	char *hname;
+
 	/* freed by policy_free */
 	if (prefix) {
-		policy->hname = kmalloc(strlen(prefix) + strlen(name) + 3,
-					gfp);
-		if (policy->hname)
-			sprintf((char *)policy->hname, "%s//%s", prefix, name);
-	} else
-		policy->hname = kstrdup(name, gfp);
-	if (!policy->hname)
+		hname = aa_str_alloc(strlen(prefix) + strlen(name) + 3, gfp);
+		if (hname)
+			sprintf(hname, "%s//%s", prefix, name);
+	} else {
+		hname = aa_str_alloc(strlen(name) + 1, gfp);
+		if (hname)
+			strcpy(hname, name);
+	}
+	if (!hname)
 		return false;
+	policy->hname = hname;
 	/* base.name is a substring of fqname */
 	policy->name = basename(policy->hname);
 	INIT_LIST_HEAD(&policy->list);
@@ -332,5 +356,5 @@ void aa_policy_destroy(struct aa_policy *policy)
 	AA_BUG(on_list_rcu(&policy->list));
 
 	/* don't free name as its a subset of hname */
-	kzfree(policy->hname);
+	aa_put_str(policy->hname);
 }

security/apparmor/policy.c

@@ -829,6 +829,14 @@ static int __lookup_replace(struct aa_ns *ns, const char *hname,
 	return 0;
 }
 
+static void share_name(struct aa_profile *old, struct aa_profile *new)
+{
+	aa_put_str(new->base.hname);
+	aa_get_str(old->base.hname);
+	new->base.hname = old->base.hname;
+	new->base.name = old->base.name;
+}
+
 /**
  * aa_replace_profiles - replace profile(s) on the profile list
  * @policy_ns: namespace load is occurring on
@@ -1013,6 +1021,7 @@ ssize_t aa_replace_profiles(struct aa_ns *policy_ns, struct aa_profile *profile,
 			     NULL, error);
 
 		if (ent->old) {
+			share_name(ent->old, ent->new);
 			__replace_profile(ent->old, ent->new, 1);
 			if (ent->rename) {
 				/* aafs interface uses proxy */