From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Date: Mon, 28 Jun 2021 16:13:43 -0300
Subject: sctp: validate chunk size in __rcv_asconf_lookup
Patch-mainline: v5.14-rc1
Git-commit: b6ffe7671b24689c09faa5675dd58f93758a97ae
References: CVE-2021-3655 bsc#1188563

In one of the fallbacks that SCTP has for identifying an association for an
incoming packet, it looks for AddIp chunk (from ASCONF) and take a peek.
Thing is, at this stage nothing was validating that the chunk actually had
enough content for that, allowing the peek to happen over uninitialized
memory.

Similar check already exists in actual asconf handling in
sctp_verify_asconf().

Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Kubecek <mkubecek@suse.cz>

---
 net/sctp/input.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -1118,6 +1118,9 @@ static struct sctp_association *__sctp_rcv_asconf_lookup(
 	union sctp_addr_param *param;
 	union sctp_addr paddr;
 
+	if (ntohs(ch->length) < sizeof(*asconf) + sizeof(struct sctp_paramhdr))
+		return NULL;
+
 	/* Skip over the ADDIP header and find the Address parameter */
 	param = (union sctp_addr_param *)(asconf + 1);