Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751925AbdITUqM (ORCPT ); Wed, 20 Sep 2017 16:46:12 -0400 Received: from mail-pf0-f181.google.com ([209.85.192.181]:49052 "EHLO mail-pf0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751826AbdITUqC (ORCPT ); Wed, 20 Sep 2017 16:46:02 -0400 X-Google-Smtp-Source: AOwi7QBQxBxW6CiwDwHyxAioBQ4iDn9rEdZKZbnUou3AZbvR9AnCwwjvv8xGEFacqVp47e0oGTZvzw== From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Kees Cook , David Windsor , Alexander Viro , linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org, linux-mm@kvack.org, kernel-hardening@lists.openwall.com Subject: [PATCH v3 06/31] vfs: Copy struct mount.mnt_id to userspace using put_user() Date: Wed, 20 Sep 2017 13:45:12 -0700 Message-Id: <1505940337-79069-7-git-send-email-keescook@chromium.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1505940337-79069-1-git-send-email-keescook@chromium.org> References: <1505940337-79069-1-git-send-email-keescook@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1293 Lines: 36 From: David Windsor The mnt_id field can be copied with put_user(), so there is no need to use copy_to_user(). In both cases, hardened usercopy is being bypassed since the size is constant, and not open to runtime manipulation. This patch is verbatim from Brad Spengler/PaX Team's PAX_USERCOPY whitelisting code in the last public patch of grsecurity/PaX based on my understanding of the code. Changes or omissions from the original code are mine and don't reflect the original grsecurity/PaX code. Signed-off-by: David Windsor [kees: adjust commit log] Cc: Alexander Viro Cc: linux-fsdevel@vger.kernel.org Signed-off-by: Kees Cook --- fs/fhandle.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/fs/fhandle.c b/fs/fhandle.c index 58a61f55e0d0..46e00ccca8f0 100644 --- a/fs/fhandle.c +++ b/fs/fhandle.c @@ -68,8 +68,7 @@ static long do_sys_name_to_handle(struct path *path, } else retval = 0; /* copy the mount id */ - if (copy_to_user(mnt_id, &real_mount(path->mnt)->mnt_id, - sizeof(*mnt_id)) || + if (put_user(real_mount(path->mnt)->mnt_id, mnt_id) || copy_to_user(ufh, handle, sizeof(struct file_handle) + handle_bytes)) retval = -EFAULT; -- 2.7.4