From 46b48062555aa5c40ee4b20740e64c7f49b85584 Mon Sep 17 00:00:00 2001
From: tuexen <tuexen@FreeBSD.org>
Date: Sat, 23 Mar 2019 22:56:03 +0000
Subject: [PATCH] Limit the size of messages sent on 1-to-many style SCTP
 sockets with the SCTP_SENDALL flag. Allow also only one operation per SCTP
 endpoint.

This fixes an issue found by running syzkaller and is joint work with rrs@.

MFC after:		1 week
---
 sys/netinet/sctp.h        |  2 ++
 sys/netinet/sctp_output.c | 13 +++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/sys/netinet/sctp.h b/sys/netinet/sctp.h
index 64fd54426382..27e5fd494fbe 100644
--- a/sys/netinet/sctp.h
+++ b/sys/netinet/sctp.h
@@ -491,6 +491,7 @@ struct sctp_error_auth_invalid_hmac {
 					 * time */
 #define SCTP_SAT_NETWORK_BURST_INCR  2	/* how many times to multiply maxburst
 					 * in sat */
+#define SCTP_MAX_SENDALL_LIMIT 1024
 
 /* Data Chuck Specific Flags */
 #define SCTP_DATA_FRAG_MASK        0x03
@@ -516,6 +517,7 @@ struct sctp_error_auth_invalid_hmac {
 #define SCTP_PCB_FLAGS_BOUNDALL		0x00000004
 #define SCTP_PCB_FLAGS_ACCEPTING	0x00000008
 #define SCTP_PCB_FLAGS_UNBOUND		0x00000010
+#define SCTP_PCB_FLAGS_SND_ITERATOR_UP  0x00000020
 #define SCTP_PCB_FLAGS_CLOSE_IP         0x00040000
 #define SCTP_PCB_FLAGS_WAS_CONNECTED    0x00080000
 #define SCTP_PCB_FLAGS_WAS_ABORTED      0x00100000
diff --git a/sys/netinet/sctp_output.c b/sys/netinet/sctp_output.c
index 1af76c3eaa64..e2661711c679 100644
--- a/sys/netinet/sctp_output.c
+++ b/sys/netinet/sctp_output.c
@@ -6804,6 +6804,10 @@ sctp_sendall_completes(void *ptr, uint32_t val SCTP_UNUSED)
 	 */
 
 	/* now free everything */
+	if (ca->inp) {
+		/* Lets clear the flag to allow others to run. */
+		ca->inp->sctp_flags &= ~SCTP_PCB_FLAGS_SND_ITERATOR_UP;
+	}
 	sctp_m_freem(ca->m);
 	SCTP_FREE(ca, SCTP_M_COPYAL);
 }
@@ -6857,6 +6861,14 @@ sctp_sendall(struct sctp_inpcb *inp, struct uio *uio, struct mbuf *m,
 	int ret;
 	struct sctp_copy_all *ca;
 
+	if (inp->sctp_flags & SCTP_PCB_FLAGS_SND_ITERATOR_UP) {
+		/* There is another. */
+		return (EBUSY);
+	}
+	if (uio->uio_resid > SCTP_MAX_SENDALL_LIMIT) {
+		/* You must be less than the max! */
+		return (EMSGSIZE);
+	}
 	SCTP_MALLOC(ca, struct sctp_copy_all *, sizeof(struct sctp_copy_all),
 	    SCTP_M_COPYAL);
 	if (ca == NULL) {
@@ -6893,6 +6905,7 @@ sctp_sendall(struct sctp_inpcb *inp, struct uio *uio, struct mbuf *m,
 			ca->sndlen += SCTP_BUF_LEN(mat);
 		}
 	}
+	inp->sctp_flags |= SCTP_PCB_FLAGS_SND_ITERATOR_UP;
 	ret = sctp_initiate_iterator(NULL, sctp_sendall_iterator, NULL,
 	    SCTP_PCB_ANY_FLAGS, SCTP_PCB_ANY_FEATURES,
 	    SCTP_ASOC_ANY_STATE,