From: Xin Long <lucien.xin@gmail.com>
Date: Wed, 20 Oct 2021 07:42:45 -0400
Subject: sctp: add vtag check in sctp_sf_violation
Patch-mainline: v5.15
Git-commit: aa0f697e45286a6b5f0ceca9418acf54b9099d99
References: CVE-2021-3772 bsc#1190351

sctp_sf_violation() is called when processing HEARTBEAT_ACK chunk
in cookie_wait state, and some other places are also using it.

The vtag in the chunk's sctphdr should be verified, otherwise, as
later in chunk length check, it may send abort with the existent
asoc's vtag, which can be exploited by one to cook a malicious
chunk to terminate a SCTP asoc.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Michal Kubecek <mkubecek@suse.cz>

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

--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -4464,6 +4464,9 @@ sctp_disposition_t sctp_sf_violation(struct net *net,
 {
 	struct sctp_chunk *chunk = arg;
 
+	if (!sctp_vtag_verify(chunk, asoc))
+		return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+
 	/* Make sure that the chunk has a valid length. */
 	if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
 		return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,