svn commit: r340897 - head/sys/kern

[Mark Johnston]

Author: markj
Date: Sat Nov 24 16:41:29 2018
New Revision: 340897
URL: https://svnweb.freebsd.org/changeset/base/340897

Log:
  Lock the knlist before releasing the in-flux state in knote_fork().
  
  Otherwise there is a window, before iteration is resumed, during which
  the knote may be freed.  The in-flux state ensures that the knote will
  not be removed from the knlist while locks are dropped.
  
  PR:		228858
  Reviewed by:	kib
  Tested by:	pho
  MFC after:	3 days
  Sponsored by:	The FreeBSD Foundation
  Differential Revision:	https://reviews.freebsd.org/D18316

Modified:
  head/sys/kern/kern_event.c

Modified: head/sys/kern/kern_event.c
==============================================================================
--- head/sys/kern/kern_event.c	Sat Nov 24 16:31:43 2018	(r340896)
+++ head/sys/kern/kern_event.c	Sat Nov 24 16:41:29 2018	(r340897)
@@ -600,10 +600,10 @@ knote_fork(struct knlist *list, int pid)
 			kn->kn_fflags |= NOTE_TRACKERR;
 		if (kn->kn_fop->f_event(kn, NOTE_FORK))
 			KNOTE_ACTIVATE(kn, 0);
+		list->kl_lock(list->kl_lockarg);
 		KQ_LOCK(kq);
 		kn_leave_flux(kn);
 		KQ_UNLOCK_FLUX(kq);
-		list->kl_lock(list->kl_lockarg);
 	}
 	list->kl_unlock(list->kl_lockarg);
 }