svn commit: r332218 - stable/11/sys/netinet

[Michael Tuexen]

Author: tuexen
Date: Sat Apr  7 20:03:35 2018
New Revision: 332218
URL: https://svnweb.freebsd.org/changeset/base/332218

Log:
  MFC r324971:
  
  Fix a bug reported by Felix Weinrank using the libfuzzer on the
  userland stack.

Modified:
  stable/11/sys/netinet/sctp_auth.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/netinet/sctp_auth.c
==============================================================================
--- stable/11/sys/netinet/sctp_auth.c	Sat Apr  7 20:02:08 2018	(r332217)
+++ stable/11/sys/netinet/sctp_auth.c	Sat Apr  7 20:03:35 2018	(r332218)
@@ -1606,9 +1606,9 @@ sctp_zero_m(struct mbuf *m, uint32_t m_offset, uint32_
 	/* now use the rest of the mbuf chain */
 	while ((m_tmp != NULL) && (size > 0)) {
 		data = mtod(m_tmp, uint8_t *)+m_offset;
-		if (size > (uint32_t)SCTP_BUF_LEN(m_tmp)) {
-			memset(data, 0, SCTP_BUF_LEN(m_tmp));
-			size -= SCTP_BUF_LEN(m_tmp);
+		if (size > (uint32_t)(SCTP_BUF_LEN(m_tmp) - m_offset)) {
+			memset(data, 0, SCTP_BUF_LEN(m_tmp) - m_offset);
+			size -= SCTP_BUF_LEN(m_tmp) - m_offset;
 		} else {
 			memset(data, 0, size);
 			size = 0;