svn commit: r310180 - head/sys/net

[Alan Somers]

Author: asomers
Date: Fri Dec 16 22:39:30 2016
New Revision: 310180
URL: https://svnweb.freebsd.org/changeset/base/310180

Log:
  Fix panic during lagg destruction with simultaneous status check
  
  If you run "ifconfig lagg0 destroy" and "ifconfig lagg0" at the same time a
  page fault may result. The first process will destroy ifp->if_lagg in
  lagg_clone_destroy (called by if_clone_destroy). Then the second process
  will observe that ifp->if_lagg is NULL at the top of lagg_port_ioctl and
  goto fallback: where it will promptly dereference ifp->if_lagg anyway.
  
  The solution is to repeat the NULL check for ifp->if_lagg
  
  MFC after:	4 weeks
  Sponsored by:	Spectra Logic Corp
  Differential Revision:	https://reviews.freebsd.org/D8512

Modified:
  head/sys/net/if_lagg.c

Modified: head/sys/net/if_lagg.c
==============================================================================
--- head/sys/net/if_lagg.c	Fri Dec 16 22:37:16 2016	(r310179)
+++ head/sys/net/if_lagg.c	Fri Dec 16 22:39:30 2016	(r310180)
@@ -252,6 +252,7 @@ SYSCTL_INT(_net_link_lagg, OID_AUTO, def
     &VNET_NAME(def_flowid_shift), 0,
     "Default setting for flowid shift for load sharing");
 
+#pragma clang optimize off
 static void
 vnet_lagg_init(const void *unused __unused)
 {
@@ -1022,7 +1023,7 @@ lagg_port_ioctl(struct ifnet *ifp, u_lon
 	return (error);
 
 fallback:
-	if (lp->lp_ioctl != NULL)
+	if (lp != NULL && lp->lp_ioctl != NULL)
 		return ((*lp->lp_ioctl)(ifp, cmd, data));
 
 	return (EINVAL);