selinux/stable-4.20 PR 20181115

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Merge tag 'selinux-pr-20181115' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux

Pull SELinux fixes from Paul Moore:
 "Two small SELinux fixes for v4.20.

  Ondrej's patch adds a check on user input, and my patch ensures we
  don't look past the end of a buffer.

  Both patches are quite small and pass the selinux-testsuite"

* tag 'selinux-pr-20181115' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
  selinux: fix non-MLS handling in mls_context_to_sid()
  selinux: check length properly in SCTP bind hook

security/selinux/hooks.c

@@ -5318,6 +5318,9 @@ static int selinux_sctp_bind_connect(struct sock *sk, int optname,
 	addr_buf = address;
 
 	while (walk_size < addrlen) {
+		if (walk_size + sizeof(sa_family_t) > addrlen)
+			return -EINVAL;
+
 		addr = addr_buf;
 		switch (addr->sa_family) {
 		case AF_UNSPEC:

security/selinux/ss/mls.c

@@ -245,9 +245,13 @@ int mls_context_to_sid(struct policydb *pol,
 	char *rangep[2];
 
 	if (!pol->mls_enabled) {
-		if ((def_sid != SECSID_NULL && oldc) || (*scontext) == '\0')
-			return 0;
-		return -EINVAL;
+		/*
+		 * With no MLS, only return -EINVAL if there is a MLS field
+		 * and it did not come from an xattr.
+		 */
+		if (oldc && def_sid == SECSID_NULL)
+			return -EINVAL;
+		return 0;
 	}
 
 	/*