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@xxxxxxxxxxxxxxx> know about it. >From foo@baz Thu Oct 19 13:36:51 CEST 2017 From: Dan Carpenter <dan.carpenter@xxxxxxxxxx> 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@xxxxxxxxxx> [ 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@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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@xxxxxxxxxx are queue-4.4/sctp-potential-read-out-of-bounds-in-sctp_ulpevent_type_enabled.patch