svn commit: r311467 - stable/11/contrib/bsnmp/snmp_mibII

[Ngie Cooper]

Author: ngie
Date: Fri Jan  6 03:54:26 2017
New Revision: 311467
URL: https://svnweb.freebsd.org/changeset/base/311467

Log:
  MFC r310873:
  
  Guard against use-after-free after calling mibif_free(..)
  
  Set variables to NULL after calling free.
  
  Also, remove unnecessary if (x != NULL) checks before calling free(x)

Modified:
  stable/11/contrib/bsnmp/snmp_mibII/mibII.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/contrib/bsnmp/snmp_mibII/mibII.c
==============================================================================
--- stable/11/contrib/bsnmp/snmp_mibII/mibII.c	Fri Jan  6 03:53:44 2017	(r311466)
+++ stable/11/contrib/bsnmp/snmp_mibII/mibII.c	Fri Jan  6 03:54:26 2017	(r311467)
@@ -707,10 +707,11 @@ mibif_free(struct mibif *ifp)
 	}
 
 	free(ifp->private);
-	if (ifp->physaddr != NULL)
-		free(ifp->physaddr);
-	if (ifp->specmib != NULL)
-		free(ifp->specmib);
+	ifp->private = NULL;
+	free(ifp->physaddr);
+	ifp->physaddr = NULL;
+	free(ifp->specmib);
+	ifp->specmib = NULL;
 
 	STAILQ_FOREACH(map, &mibindexmap_list, link)
 		if (map->mibif == ifp) {
@@ -745,8 +746,8 @@ mibif_free(struct mibif *ifp)
 		at = at1;
 	}
 
-
 	free(ifp);
+	ifp = NULL;
 	mib_if_number--;
 	mib_iftable_last_change = this_tick;
 }