From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CAF39C2D0A8 for ; Sat, 26 Sep 2020 07:46:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 83C592080A for ; Sat, 26 Sep 2020 07:46:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728967AbgIZHqy convert rfc822-to-8bit (ORCPT ); Sat, 26 Sep 2020 03:46:54 -0400 Received: from coyote.holtmann.net ([212.227.132.17]:38708 "EHLO mail.holtmann.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726149AbgIZHqy (ORCPT ); Sat, 26 Sep 2020 03:46:54 -0400 Received: from [172.20.10.2] (dynamic-046-114-136-219.46.114.pool.telefonica.de [46.114.136.219]) by mail.holtmann.org (Postfix) with ESMTPSA id 52A45CECE8; Sat, 26 Sep 2020 09:53:50 +0200 (CEST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.1\)) Subject: Re: [Linux-kernel-mentees] [PATCH] Fix uninit-value in hci_chan_lookup_handle From: Marcel Holtmann In-Reply-To: <20200905020410.20350-1-anant.thazhemadam@gmail.com> Date: Sat, 26 Sep 2020 09:46:49 +0200 Cc: linux-kernel-mentees@lists.linuxfoundation.org, Johan Hedberg , linux-bluetooth , linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8BIT Message-Id: <2AEF86AF-8F80-4B01-B506-D2ABC654DBC7@holtmann.org> References: <20200905020410.20350-1-anant.thazhemadam@gmail.com> To: Anant Thazhemadam X-Mailer: Apple Mail (2.3608.120.23.2.1) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Anant, > When the amount of data stored in the location corresponding to > iov_iter *from is less then 4, some data seems to go uninitialized. > > Updating this condition accordingly, makes sense both intuitively and > logically as well, since the other check for extreme condition done is if > len > HCI_MAX_FRAME_SIZE, which is HCI_MAX_ACL_SIZE (which is 1024) + 4; > which itself gives some idea about what must be the ideal mininum size. > > Reported-and-tested by: syzbot+4c14a8f574461e1c3659@syzkaller.appspotmail.com > Signed-off-by: Anant Thazhemadam > --- > If there is some explicit reason why len < 4 doesn't work, and only len < 2 works, > please do let me know. > The commit message that introduced the initial change > (512b2268156a4e15ebf897f9a883bdee153a54b7) wasn't exactly very helpful in this > respect, and I couldn't find a whole lot of discussion regarding this either. > > drivers/bluetooth/hci_vhci.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/bluetooth/hci_vhci.c b/drivers/bluetooth/hci_vhci.c > index 8ab26dec5f6e..0c49821d7b98 100644 > --- a/drivers/bluetooth/hci_vhci.c > +++ b/drivers/bluetooth/hci_vhci.c > @@ -159,7 +159,7 @@ static inline ssize_t vhci_get_user(struct vhci_data *data, > __u8 pkt_type, opcode; > int ret; > > - if (len < 2 || len > HCI_MAX_FRAME_SIZE) > + if (len < 4 || len > HCI_MAX_FRAME_SIZE) > return -EINVAL; so the minimum requirement is to have an 1 octet packet indicator. If some other functions are missing length checks, then it should be fixed there. I see that in case of HCI_VENDOR_PKT we need to check for the 2nd octet to be present, but I have no idea why you require 3 octets minimum. As I said, if so, then the other functions that get called require proper range checks. Regards Marcel