svn commit: r364220 - head/sys/net

[Bryan Drewery]

Author: bdrewery
Date: Thu Aug 13 22:06:27 2020
New Revision: 364220
URL: https://svnweb.freebsd.org/changeset/base/364220

Log:
  lagg: Avoid adding a port to a lagg device being destroyed.
  
  The lagg_clone_destroy() handles detach and waiting for ifconfig callers
  to drain already.
  
  This narrows the race for 2 panics that the tests triggered. Both were a
  consequence of adding a port to the lagg device after it had already detached
  from all of its ports. The link state task would run after lagg_clone_destroy()
  free'd the lagg softc.
  
      kernel:trap_fatal+0xa4
      kernel:trap_pfault+0x61
      kernel:trap+0x316
      kernel:witness_checkorder+0x6d
      kernel:_sx_xlock+0x72
      if_lagg.ko:lagg_port_state+0x3b
      kernel:if_down+0x144
      kernel:if_detach+0x659
      if_tap.ko:tap_destroy+0x46
      kernel:if_clone_destroyif+0x1b7
      kernel:if_clone_destroy+0x8d
      kernel:ifioctl+0x29c
      kernel:kern_ioctl+0x2bd
      kernel:sys_ioctl+0x16d
      kernel:amd64_syscall+0x337
  
      kernel:trap_fatal+0xa4
      kernel:trap_pfault+0x61
      kernel:trap+0x316
      kernel:witness_checkorder+0x6d
      kernel:_sx_xlock+0x72
      if_lagg.ko:lagg_port_state+0x3b
      kernel:do_link_state_change+0x9b
      kernel:taskqueue_run_locked+0x10b
      kernel:taskqueue_run+0x49
      kernel:ithread_loop+0x19c
      kernel:fork_exit+0x83
  
  PR:		244168
  Reviewed by:	markj
  MFC after:	2 weeks
  Sponsored by:	Dell EMC
  Differential Revision:	https://reviews.freebsd.org/D25284

Modified:
  head/sys/net/if_lagg.c

Modified: head/sys/net/if_lagg.c
==============================================================================
--- head/sys/net/if_lagg.c	Thu Aug 13 20:48:14 2020	(r364219)
+++ head/sys/net/if_lagg.c	Thu Aug 13 22:06:27 2020	(r364220)
@@ -679,6 +679,9 @@ lagg_port_create(struct lagg_softc *sc, struct ifnet *
 		return (EINVAL);
 	}
 
+	if (sc->sc_destroying == 1)
+		return (ENXIO);
+
 	/* Limit the maximal number of lagg ports */
 	if (sc->sc_count >= LAGG_MAX_PORTS)
 		return (ENOSPC);
@@ -1190,6 +1193,8 @@ lagg_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data
 	int count, buflen, len, error = 0, oldmtu;
 
 	bzero(&rpbuf, sizeof(rpbuf));
+
+	/* XXX: This can race with lagg_clone_destroy. */
 
 	switch (cmd) {
 	case SIOCGLAGG: