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From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Sun, 6 Jul 2014 23:01:30 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r268341 - stable/10/sys/kern
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Author: mjg
Date: Sun Jul  6 23:01:29 2014
New Revision: 268341
URL: http://svnweb.freebsd.org/changeset/base/268341

Log:
  MFC r267947:
  
  Check lower bound of cmsg_len.
  
  If passed cm->cmsg_len was below cmsghdr size the experssion:
  datalen = (caddr_t)cm + cm->cmsg_len - (caddr_t)data;
  
  would give negative result. However, in practice it would not
  result in a crash because the kernel would try to obtain garbage fds
  for given process and would error out with EBADF.
  
  PR:		124908
  Submitted by:	campbell mumble.net (modified a little)

Modified:
  stable/10/sys/kern/uipc_usrreq.c

Modified: stable/10/sys/kern/uipc_usrreq.c
==============================================================================
--- stable/10/sys/kern/uipc_usrreq.c	Sun Jul  6 22:58:53 2014	(r268340)
+++ stable/10/sys/kern/uipc_usrreq.c	Sun Jul  6 23:01:29 2014	(r268341)
@@ -1859,7 +1859,7 @@ unp_internalize(struct mbuf **controlp, 
 	*controlp = NULL;
 	while (cm != NULL) {
 		if (sizeof(*cm) > clen || cm->cmsg_level != SOL_SOCKET
-		    || cm->cmsg_len > clen) {
+		    || cm->cmsg_len > clen || cm->cmsg_len < sizeof(*cm)) {
 			error = EINVAL;
 			goto out;
 		}