apparmor: make computing policy hashes conditional on kernel parameter

Allow turning off the computation of the policy hashes via the
apparmor.hash_policy kernel parameter.
Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/lsm.c

@@ -166,42 +166,42 @@ static int common_perm(const char *op, const struct path *path, u32 mask,
 }
 
 /**
- * common_perm_dir_dentry - common permission wrapper when path is dir, dentry
+ * common_perm_cond - common permission wrapper around inode cond
  * @op: operation being checked
- * @dir: directory of the dentry  (NOT NULL)
- * @dentry: dentry to check  (NOT NULL)
+ * @path: location to check (NOT NULL)
  * @mask: requested permissions mask
- * @cond: conditional info for the permission request  (NOT NULL)
  *
  * Returns: %0 else error code if error or permission denied
  */
-static int common_perm_dir_dentry(const char *op, const struct path *dir,
-				  struct dentry *dentry, u32 mask,
-				  struct path_cond *cond)
+static int common_perm_cond(const char *op, const struct path *path, u32 mask)
 {
-	struct path path = { .mnt = dir->mnt, .dentry = dentry };
+	struct path_cond cond = { d_backing_inode(path->dentry)->i_uid,
+				  d_backing_inode(path->dentry)->i_mode
+	};
 
-	return common_perm(op, &path, mask, cond);
+	if (!path_mediated_fs(path->dentry))
+		return 0;
+
+	return common_perm(op, path, mask, &cond);
 }
 
 /**
- * common_perm_path - common permission wrapper when mnt, dentry
+ * common_perm_dir_dentry - common permission wrapper when path is dir, dentry
  * @op: operation being checked
- * @path: location to check (NOT NULL)
+ * @dir: directory of the dentry  (NOT NULL)
+ * @dentry: dentry to check  (NOT NULL)
  * @mask: requested permissions mask
+ * @cond: conditional info for the permission request  (NOT NULL)
  *
  * Returns: %0 else error code if error or permission denied
  */
-static inline int common_perm_path(const char *op, const struct path *path,
-				   u32 mask)
+static int common_perm_dir_dentry(const char *op, const struct path *dir,
+				  struct dentry *dentry, u32 mask,
+				  struct path_cond *cond)
 {
-	struct path_cond cond = { d_backing_inode(path->dentry)->i_uid,
-				  d_backing_inode(path->dentry)->i_mode
-	};
-	if (!path_mediated_fs(path->dentry))
-		return 0;
+	struct path path = { .mnt = dir->mnt, .dentry = dentry };
 
-	return common_perm(op, path, mask, &cond);
+	return common_perm(op, &path, mask, cond);
 }
 
 /**
@@ -274,7 +274,7 @@ static int apparmor_path_mknod(const struct path *dir, struct dentry *dentry,
 
 static int apparmor_path_truncate(const struct path *path)
 {
-	return common_perm_path(OP_TRUNC, path, MAY_WRITE | AA_MAY_META_WRITE);
+	return common_perm_cond(OP_TRUNC, path, MAY_WRITE | AA_MAY_META_WRITE);
 }
 
 static int apparmor_path_symlink(const struct path *dir, struct dentry *dentry,
@@ -333,17 +333,17 @@ static int apparmor_path_rename(const struct path *old_dir, struct dentry *old_d
 
 static int apparmor_path_chmod(const struct path *path, umode_t mode)
 {
-	return common_perm_path(OP_CHMOD, path, AA_MAY_CHMOD);
+	return common_perm_cond(OP_CHMOD, path, AA_MAY_CHMOD);
 }
 
 static int apparmor_path_chown(const struct path *path, kuid_t uid, kgid_t gid)
 {
-	return common_perm_path(OP_CHOWN, path, AA_MAY_CHOWN);
+	return common_perm_cond(OP_CHOWN, path, AA_MAY_CHOWN);
 }
 
 static int apparmor_inode_getattr(const struct path *path)
 {
-	return common_perm_path(OP_GETATTR, path, AA_MAY_META_READ);
+	return common_perm_cond(OP_GETATTR, path, AA_MAY_META_READ);
 }
 
 static int apparmor_file_open(struct file *file, const struct cred *cred)

security/apparmor/policy_unpack.c

@@ -825,6 +825,7 @@ int aa_unpack(struct aa_loaddata *udata, struct list_head *lh,
 		if (error)
 			goto fail_profile;
 
+		if (aa_g_hash_policy)
 			error = aa_calc_profile_hash(profile, e.version, start,
 						     e.pos - start);
 		if (error)
@@ -841,12 +842,14 @@ int aa_unpack(struct aa_loaddata *udata, struct list_head *lh,
 		list_add_tail(&ent->list, lh);
 	}
 	udata->abi = e.version & K_ABI_MASK;
+	if (aa_g_hash_policy) {
 		udata->hash = aa_calc_hash(udata->data, udata->size);
 		if (IS_ERR(udata->hash)) {
 			error = PTR_ERR(udata->hash);
 			udata->hash = NULL;
 			goto fail;
 		}
+	}
 	return 0;
 
 fail_profile: