From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:37378 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728901AbeKZVzB (ORCPT ); Mon, 26 Nov 2018 16:55:01 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+72473edc9bf4eb1c6556@syzkaller.appspotmail.com, Jann Horn , Andy Lutomirski , Eric Biggers , Jiri Kosina Subject: [PATCH 4.14 61/62] HID: uhid: forbid UHID_CREATE under KERNEL_DS or elevated privileges Date: Mon, 26 Nov 2018 11:51:42 +0100 Message-Id: <20181126105055.130476030@linuxfoundation.org> In-Reply-To: <20181126105050.592727680@linuxfoundation.org> References: <20181126105050.592727680@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Biggers commit 8c01db7619f07c85c5cd81ec5eb83608b56c88f5 upstream. When a UHID_CREATE command is written to the uhid char device, a copy_from_user() is done from a user pointer embedded in the command. When the address limit is KERNEL_DS, e.g. as is the case during sys_sendfile(), this can read from kernel memory. Alternatively, information can be leaked from a setuid binary that is tricked to write to the file descriptor. Therefore, forbid UHID_CREATE in these cases. No other commands in uhid_char_write() are affected by this bug and UHID_CREATE is marked as "obsolete", so apply the restriction to UHID_CREATE only rather than to uhid_char_write() entirely. Thanks to Dmitry Vyukov for adding uhid definitions to syzkaller and to Jann Horn for commit 9da3f2b740544 ("x86/fault: BUG() when uaccess helpers fault on kernel addresses"), allowing this bug to be found. Reported-by: syzbot+72473edc9bf4eb1c6556@syzkaller.appspotmail.com Fixes: d365c6cfd337 ("HID: uhid: add UHID_CREATE and UHID_DESTROY events") Cc: # v3.6+ Cc: Jann Horn Cc: Andy Lutomirski Signed-off-by: Eric Biggers Reviewed-by: Jann Horn Signed-off-by: Jiri Kosina Signed-off-by: Greg Kroah-Hartman --- drivers/hid/uhid.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) --- a/drivers/hid/uhid.c +++ b/drivers/hid/uhid.c @@ -12,6 +12,7 @@ #include #include +#include #include #include #include @@ -722,6 +723,17 @@ static ssize_t uhid_char_write(struct fi switch (uhid->input_buf.type) { case UHID_CREATE: + /* + * 'struct uhid_create_req' contains a __user pointer which is + * copied from, so it's unsafe to allow this with elevated + * privileges (e.g. from a setuid binary) or via kernel_write(). + */ + if (file->f_cred != current_cred() || uaccess_kernel()) { + pr_err_once("UHID_CREATE from different security context by process %d (%s), this is not allowed.\n", + task_tgid_vnr(current), current->comm); + ret = -EACCES; + goto unlock; + } ret = uhid_dev_create(uhid, &uhid->input_buf); break; case UHID_CREATE2: