Patch "sctp: potential read out of bounds in sctp_ulpevent_type_enabled()" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    sctp: potential read out of bounds in sctp_ulpevent_type_enabled()

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     sctp-potential-read-out-of-bounds-in-sctp_ulpevent_type_enabled.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Thu Oct 19 13:36:51 CEST 2017
From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Thu, 14 Sep 2017 02:00:54 +0300
Subject: sctp: potential read out of bounds in sctp_ulpevent_type_enabled()

From: Dan Carpenter <dan.carpenter@oracle.com>


[ Upstream commit fa5f7b51fc3080c2b195fa87c7eca7c05e56f673 ]

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 <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/net/sctp/ulpevent.h |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/include/net/sctp/ulpevent.h
+++ b/include/net/sctp/ulpevent.h
@@ -141,8 +141,12 @@ __u16 sctp_ulpevent_get_notification_typ
 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? */


Patches currently in stable-queue which might be from dan.carpenter@oracle.com are

queue-4.4/sctp-potential-read-out-of-bounds-in-sctp_ulpevent_type_enabled.patch