From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:41816 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730545AbfHWJ3f (ORCPT ); Fri, 23 Aug 2019 05:29:35 -0400 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x7N9RLqN008033 for ; Fri, 23 Aug 2019 05:29:34 -0400 Received: from e06smtp04.uk.ibm.com (e06smtp04.uk.ibm.com [195.75.94.100]) by mx0b-001b2d01.pphosted.com with ESMTP id 2ujd6s8sfk-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 23 Aug 2019 05:29:33 -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 10:29:32 +0100 From: Julian Wiedmann Subject: [PATCH net] s390/qeth: reject oversized SNMP requests Date: Fri, 23 Aug 2019 11:29:23 +0200 Message-Id: <20190823092923.8507-1-jwi@linux.ibm.com> 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 , Julian Wiedmann 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; -- 2.17.1