From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:40936 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726634AbfHWJcC (ORCPT ); Fri, 23 Aug 2019 05:32:02 -0400 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x7N9RFau029188 for ; Fri, 23 Aug 2019 05:32:00 -0400 Received: from e06smtp04.uk.ibm.com (e06smtp04.uk.ibm.com [195.75.94.100]) by mx0a-001b2d01.pphosted.com with ESMTP id 2ujd139cvg-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 23 Aug 2019 05:32:00 -0400 Received: from localhost by e06smtp04.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 23 Aug 2019 10:31:58 +0100 Subject: Re: [PATCH net] s390/qeth: reject oversized SNMP requests References: <20190823092923.8507-1-jwi@linux.ibm.com> From: Julian Wiedmann Date: Fri, 23 Aug 2019 11:31:53 +0200 MIME-Version: 1.0 In-Reply-To: <20190823092923.8507-1-jwi@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Message-Id: Sender: linux-s390-owner@vger.kernel.org List-ID: To: David Miller Cc: netdev@vger.kernel.org, linux-s390@vger.kernel.org, Heiko Carstens , Stefan Raspl , Ursula Braun , Dan Carpenter +cc Dan On 23.08.19 11:29, Julian Wiedmann wrote: > Commit d4c08afafa04 ("s390/qeth: streamline SNMP cmd code") removed > the bounds checking for req_len, under the assumption that the check in > qeth_alloc_cmd() would suffice. > > But that code path isn't sufficiently robust to handle a user-provided > data_length, which could overflow (when adding the cmd header overhead) > before being checked against QETH_BUFSIZE. We end up allocating just a > tiny iob, and the subsequent copy_from_user() writes past the end of > that iob. > > Special-case this path and add a coarse bounds check, to protect against > maliciuous requests. This let's the subsequent code flow do its normal > job and precise checking, without risk of overflow. > > Fixes: d4c08afafa04 ("s390/qeth: streamline SNMP cmd code") > Reported-by: Dan Carpenter > Signed-off-by: Julian Wiedmann > Reviewed-by: Ursula Braun > --- > drivers/s390/net/qeth_core_main.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c > index 9c3310c4d61d..6502b148541e 100644 > --- a/drivers/s390/net/qeth_core_main.c > +++ b/drivers/s390/net/qeth_core_main.c > @@ -4374,6 +4374,10 @@ static int qeth_snmp_command(struct qeth_card *card, char __user *udata) > get_user(req_len, &ureq->hdr.req_len)) > return -EFAULT; > > + /* Sanitize user input, to avoid overflows in iob size calculation: */ > + if (req_len > QETH_BUFSIZE) > + return -EINVAL; > + > iob = qeth_get_adapter_cmd(card, IPA_SETADP_SET_SNMP_CONTROL, req_len); > if (!iob) > return -ENOMEM; >