From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934119AbdKAVxO (ORCPT ); Wed, 1 Nov 2017 17:53:14 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:35290 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934079AbdKAV1t (ORCPT ); Wed, 1 Nov 2017 17:27:49 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Dan Carpenter , "David S . Miller" , Greg Kroah-Hartman , Willy Tarreau Subject: [PATCH 3.10 078/139] sctp: potential read out of bounds in sctp_ulpevent_type_enabled() Date: Wed, 1 Nov 2017 22:26:19 +0100 Message-Id: <1509571600-4858-29-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1509571600-4858-1-git-send-email-w@1wt.eu> References: <1509571159-4405-1-git-send-email-w@1wt.eu> <1509571600-4858-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dan Carpenter commit fa5f7b51fc3080c2b195fa87c7eca7c05e56f673 upstream. This code causes a static checker warning because Smatch doesn't trust anything that comes from skb->data. I've reviewed this code and I do think skb->data can be controlled by the user here. The sctp_event_subscribe struct has 13 __u8 fields and we want to see if ours is non-zero. sn_type can be any value in the 0-USHRT_MAX range. We're subtracting SCTP_SN_TYPE_BASE which is 1 << 15 so we could read either before the start of the struct or after the end. This is a very old bug and it's surprising that it would go undetected for so long but my theory is that it just doesn't have a big impact so it would be hard to notice. Signed-off-by: Dan Carpenter Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman Signed-off-by: Willy Tarreau --- include/net/sctp/ulpevent.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/include/net/sctp/ulpevent.h b/include/net/sctp/ulpevent.h index ca4693b..00c0e5b 100644 --- a/include/net/sctp/ulpevent.h +++ b/include/net/sctp/ulpevent.h @@ -143,8 +143,12 @@ __u16 sctp_ulpevent_get_notification_type(const struct sctp_ulpevent *event); static inline int sctp_ulpevent_type_enabled(__u16 sn_type, struct sctp_event_subscribe *mask) { + int offset = sn_type - SCTP_SN_TYPE_BASE; char *amask = (char *) mask; - return amask[sn_type - SCTP_SN_TYPE_BASE]; + + if (offset >= sizeof(struct sctp_event_subscribe)) + return 0; + return amask[offset]; } /* Given an event subscription, is this event enabled? */ -- 2.8.0.rc2.1.gbe9624a