Smack: ignore private inode for smack_file_receive

The dmabuf fd can be shared between processes via unix domain
socket. The file of dmabuf fd is came from anon_inode. The inode
has no set and get xattr operations, so it can not be shared
between processes with smack. This patch fixes just to ignore
private inode including anon_inode for smack_file_receive.
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>

security/smack/smack_lsm.c

@@ -1658,6 +1658,9 @@ static int smack_file_receive(struct file *file)
 	struct smk_audit_info ad;
 	struct inode *inode = file_inode(file);
 
+	if (unlikely(IS_PRIVATE(inode)))
+		return 0;
+
 	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_PATH);
 	smk_ad_setfield_u_fs_path(&ad, file->f_path);
 	/*