lsm: Refactor return value of LSM hook inode_copy_up_xattr

To be consistent with most LSM hooks, convert the return value of
hook inode_copy_up_xattr to 0 or a negative error code.

Before:
- Hook inode_copy_up_xattr returns 0 when accepting xattr, 1 when
  discarding xattr, -EOPNOTSUPP if it does not know xattr, or any
  other negative error code otherwise.

After:
- Hook inode_copy_up_xattr returns 0 when accepting xattr, *-ECANCELED*
  when discarding xattr, -EOPNOTSUPP if it does not know xattr, or
  any other negative error code otherwise.
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

fs/overlayfs/copy_up.c

@@ -115,12 +115,12 @@ int ovl_copy_xattr(struct super_block *sb, const struct path *oldpath, struct de
 			continue;
 
 		error = security_inode_copy_up_xattr(old, name);
-		if (error < 0 && error != -EOPNOTSUPP)
-			break;
-		if (error == 1) {
+		if (error == -ECANCELED) {
 			error = 0;
 			continue; /* Discard */
 		}
+		if (error < 0 && error != -EOPNOTSUPP)
+			break;
 
 		if (is_posix_acl_xattr(name)) {
 			error = ovl_copy_acl(OVL_FS(sb), oldpath, new, name);

security/integrity/evm/evm_main.c

@@ -1000,7 +1000,7 @@ static int evm_inode_copy_up_xattr(struct dentry *src, const char *name)
 	case EVM_XATTR_HMAC:
 	case EVM_IMA_XATTR_DIGSIG:
 	default:
-		rc = 1; /* discard */
+		rc = -ECANCELED; /* discard */
 	}
 
 	kfree(xattr_data);

security/security.c

@@ -2674,19 +2674,14 @@ EXPORT_SYMBOL(security_inode_copy_up);
  * lower layer to the union/overlay layer.   The caller is responsible for
  * reading and writing the xattrs, this hook is merely a filter.
  *
- * Return: Returns 0 to accept the xattr, 1 to discard the xattr, -EOPNOTSUPP
- *         if the security module does not know about attribute, or a negative
- *         error code to abort the copy up.
+ * Return: Returns 0 to accept the xattr, -ECANCELED to discard the xattr,
+ *         -EOPNOTSUPP if the security module does not know about attribute,
+ *         or a negative error code to abort the copy up.
  */
 int security_inode_copy_up_xattr(struct dentry *src, const char *name)
 {
 	int rc;
 
-	/*
-	 * The implementation can return 0 (accept the xattr), 1 (discard the
-	 * xattr), -EOPNOTSUPP if it does not know anything about the xattr or
-	 * any other error code in case of an error.
-	 */
 	rc = call_int_hook(inode_copy_up_xattr, src, name);
 	if (rc != LSM_RET_DEFAULT(inode_copy_up_xattr))
 		return rc;

security/selinux/hooks.c

@@ -3531,8 +3531,8 @@ static int selinux_inode_copy_up_xattr(struct dentry *dentry, const char *name)
 	 * xattrs up.  Instead, filter out SELinux-related xattrs following
 	 * policy load.
 	 */
-	if (selinux_initialized() && strcmp(name, XATTR_NAME_SELINUX) == 0)
-		return 1; /* Discard */
+	if (selinux_initialized() && !strcmp(name, XATTR_NAME_SELINUX))
+		return -ECANCELED; /* Discard */
 	/*
 	 * Any other attribute apart from SELINUX is not claimed, supported
 	 * by selinux.

security/smack/smack_lsm.c

@@ -4910,10 +4910,10 @@ static int smack_inode_copy_up(struct dentry *dentry, struct cred **new)
 static int smack_inode_copy_up_xattr(struct dentry *src, const char *name)
 {
 	/*
-	 * Return 1 if this is the smack access Smack attribute.
+	 * Return -ECANCELED if this is the smack access Smack attribute.
 	 */
-	if (strcmp(name, XATTR_NAME_SMACK) == 0)
-		return 1;
+	if (!strcmp(name, XATTR_NAME_SMACK))
+		return -ECANCELED;
 
 	return -EOPNOTSUPP;
 }